This work was supported by the National Natural Science Foundation of China (NSFC) (Grant 62075238, 61675231) and&#160;the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB24030600).

1. Optical coupling
<ol>
	<li>Polish the end-face of the MRR on a grinding plate using 1.5 &#956;m abrasive powders (aluminum oxide) mixed with water for 5 min.</li>
	<li>Fix the MRR with a chip fixture and place an eight-channel FA on a six-axis coupling stage, which includes three linear stages with a resolution of 50 nm and three angle stages with a resolution of 0.003&#176;. The patches of the MRR and FA are 250 &#956;m.</li>
	<li>Use a 1,550 nm laser as an optical source for real-time monitoring of the coupling efficiency. Carefully adjust the position of the FA until the inset loss reaches the minimum value, typically less than 6 dB, corresponding to a coupling loss of less than 3 dB per facet.</li>
	<li>Use an ultraviolet (UV) curved adhesive (Table of Materials) to glue the MRR and FA. Place the adhesive on the side edge of the contact surface, which ensures that there is no glue on the optical path.</li>
	<li>Expose the UV-curved adhesive to a UV lamp for 150 s and bake in a chamber at 120 &#176;C for more than 1 h.</li>
</ol>
2. Device packaging
<ol>
	<li>Conglutinate a 10.2 mm x 6.05 mm TEC chip with a maximum power of 3.9 W to the baseplate of a standard 14-pin butterfly package using silver glue. Solder the two electrodes of the TEC chip to two pins of the butterfly package.</li>
	<li>Paste a 5 mm &#215; 5 mm &#215; 1 mm tungsten plate to the surface of the TEC chip using silver glue. Use the tungsten plate as a heat sink to fill the gap between the TEC and MRR.</li>
	<li>Paste the MRR device to the top of the tungsten plate using silver glue and fix the pigtail of the FA to the output port of the butterfly package.</li>
	<li>Paste a thermistor chip to the surface of the TEC chip using silver glue. Connect one electrode of the thermistor to the top surface of TEC chip. Wire bond the other electrode of the thermistor and the top surface of TEC chip to two pins of the butterfly package using gold thread.</li>
	<li>Bake the packaged device at 100 &#176;C for 1 h to solidify the silver glue.</li>
	<li>Seal the butterfly package. Figure 1 shows the packaged device.</li>
</ol>
3. SCs generation
<ol>
	<li>Figure 2 shows the set-up of the experiments. Use an erbium-doped fiber amplifier (EDFA) to boost the pump for micro-comb generation. Control the polarization state of the pump using a fiber polarization controller (FPC). Connect all the devices using single mode fibers (SMF).</li>
	<li>Fix the wavelength of the pump laser at 1,556.3 nm. Manually tune the operation temperature through an external commercial TEC controller.</li>
	<li>Monitor the output optical spectrum with an optical spectrum analyzer. Detect the output power trace with a 3 GHz photodetector and record with an oscilloscope.</li>
	<li>Set the output of the EDFA to 34 dBm, corresponding to an on-chip power of 30.5 dBm (considering the coupling loss of the MRR and FA, insert loss of the FPC), which ensures that there is enough power coupled into the MRR for micro-comb generation.</li>
	<li>Set the thermistor to 2 k&#937;, corresponding to an operating temperature of 66 &#176;C. Then slowly decrease the operating temperature by changing the set value of the thermistor. In these experiments, when the thermistor was set to 5.8 k&#937;, corresponding to 38 &#176;C, one resonance of the MRR passed through the pump and a triangular shape power trace was recorded.</li>
	<li>Tune the polarization of the pump by the FPC until an SC step is observed at the falling edge of the triangular transmission power trace. Figure 3 shows a typical optical transmission power trace.</li>
	<li>Slowly decrease the operation temperature from ~66 &#176;C and stop when a palm-like optical spectrum is observed on the optical spectrum analyzer. The value of the thermistor was around 5.6 k&#937; in these experiments. Figure 4A and Figure 5B show the optical spectra of perfect SCs and SCs with a single vacancy, respectively.</li>
</ol>
4. Repetition rate fluctuation measurement
<ol>
	<li>Connect the generated SCs to a tunable bandpass filter (TBPF) to extract an individual comb line. Set the passband of the TBPF to 0.1 nm. Its central wavelength can be tuned over the full C and L band. The filter slope is 400 dB/nm.</li>
	<li>Couple the selected comb line to an asymmetric Mach-Zehnder interferometer (AMZI). The optical frequency in one arm of the AMZI is shifted by 200 MHz using an acousto-optic modulator (AOM). The optical field in the other arm is delayed by a segment of optical fiber. Delay fibers of 2 km and 25 km are used in these experiments.</li>
	<li>Detect the output optical signal with a photodiode and analyze the PSD spectrum using an electrical spectrum analyzer.</li>
	<li>Tune the central wavelength of the TBPF. Measure the PSDs of every comb line using the described method. Figure 4B,C shows the PSD spectra for comb lines S1 and S2 of perfect SCs with the 2 km and 25 km delay optical fibers, respectively.</li>
	<li>Using the same method, measure the PSD curves of SCs with a vacancy. Record the 3 dB bandwidth of the PSD curve and linearly fit it piecewise as shown in Figure 5B,C. Repetition rate fluctuations of ~53.24 Hz within 10 &#181;s and ~509.32 Hz within 125 &#181;s were derived.</li>
</ol>

<ol>
	<li>Herr, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Temporal+solitons+in+optical+microresonators.">Temporal solitons in optical microresonators.</a> Nature Photonics. 8, 145-152 (2014).</li><li>Li, J., Lee, H., Chen, T., Vahala, K. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Low-pump-power,+low-phase-noise,+and+microwave+to+millimeter-wave+repetition+rate+operation+in+microcombs.">Low-pump-power, low-phase-noise, and microwave to millimeter-wave repetition rate operation in microcombs.</a> Physical Review Letters. 109, 1-5 (2012).</li><li>Trocha, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrafast+optical+ranging+using+microresonator+soliton+frequency+combs.">Ultrafast optical ranging using microresonator soliton frequency combs.</a> Science. 359, 887-891 (2018).</li><li>Myoung-Gyun, S., Qi-Fan, Y., Ki Youl, Y., Xu, Y., Kerry, L. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microresonator+soliton+dual-comb+spectroscopy.">Microresonator soliton dual-comb spectroscopy.</a> Science. 354, 600-603 (2016).</li><li>Marin-Palomo, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microresonator-based+solitons+for+massively+parallel+coherent+optical+communications.">Microresonator-based solitons for massively parallel coherent optical communications.</a> Nature. 546, 274-279 (2017).</li><li>Fang-Xiang, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantum+key+distribution+with+dissipative+Kerr+soliton+generated+by+on-chip+microresonators.">Quantum key distribution with dissipative Kerr soliton generated by on-chip microresonators.</a> arXiv. , (2018).</li><li>Spencer, D. T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+optical-frequency+synthesizer+using+integrated+photonics.">An optical-frequency synthesizer using integrated photonics.</a> Nature. 557, 81-85 (2018).</li><li>Del'Haye, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phase-coherent+microwave-to-optical+link+with+a+self-referenced+microcomb.">Phase-coherent microwave-to-optical link with a self-referenced microcomb.</a> Nature Photonics. 10, 516-520 (2016).</li><li>Huang, S. W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+broadband+chip-scale+optical+frequency+synthesizer+at+2.7x10-16+relative+uncertainty.">A broadband chip-scale optical frequency synthesizer at 2.7x10-16 relative uncertainty.</a> Science Advance. 2, 1501489 (2016).</li><li>Liang, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High+spectral+purity+Kerr+frequency+comb+radio+frequency+photonic+oscillator.">High spectral purity Kerr frequency comb radio frequency photonic oscillator.</a> Nature Communications. 6, 7957 (2015).</li><li>Liao, P. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dependence+of+a+microresonator+Kerr+frequency+comb+on+the+pump+linewidth.">Dependence of a microresonator Kerr frequency comb on the pump linewidth.</a> Optics Letters. 42, 779-782 (2017).</li><li>Wang, W. Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Robust+soliton+crystals+in+a+thermally+controlled+microresonator.">Robust soliton crystals in a thermally controlled microresonator.</a> Optics Letters. 43, 2002-2005 (2018).</li><li>Chaitanya, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermally+controlled+comb+generation+and+soliton+modelocking+in+microresonators.">Thermally controlled comb generation and soliton modelocking in microresonators.</a> Optics Letters. 41, 2565-2568 (2016).</li><li>Lu, Z. Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Deterministic+generation+and+switching+of+dissipative+Kerr+soliton+in+a+thermally+controlled+micro-resonator.">Deterministic generation and switching of dissipative Kerr soliton in a thermally controlled micro-resonator.</a> AIP Advances. 9, 025314 (2019).</li><li>Jost, J. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Counting+the+Cycles+of+Light+using+a+Self-Referenced+Optical+Microresonator.">Counting the Cycles of Light using a Self-Referenced Optical Microresonator.</a> Optica. 2, 706-711 (2014).</li><li>Brasch, V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Self-referenced+photonic+chip+soliton+Kerr+frequency+comb.">Self-referenced photonic chip soliton Kerr frequency comb.</a> Light: Science &amp; Applications. 6, 16202-16206 (2017).</li><li>Cole, D. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Soliton+crystals+in+Kerr+resonators.">Soliton crystals in Kerr resonators.</a> Nature Photonics. 11, 671-676 (2017).</li><li>Little, B. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+VLSI+photonics+platform.">A VLSI photonics platform.</a> Conference on Optical Fiber Communication. 86, 444-445 (2003).</li><li>Wang, W. Q., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dual-pump+kerr+micro-cavity+optical+frequency+comb+with+varying+FSR+spacing.">Dual-pump kerr micro-cavity optical frequency comb with varying FSR spacing.</a> Scientific Report. 6, 28501 (2016).</li><li>Kessler, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+sub-40-m+Hz-linewidth+laser+based+on+a+silicon+single-crystal+optical+cavity.">A sub-40-m Hz-linewidth laser based on a silicon single-crystal optical cavity.</a> Nature Photonics. 6, 687-692 (2012).</li></ol>

The authors declare that they have no competing financial interests.

On-chip DKSs provide novel compact coherent optical sources and exhibit excellent application prospects in optical metrology, molecular spectroscopy, and other functions. For commercial applications, compact packaged micro-comb sources are essential. This protocol provides a practical approach to make a packaged micro-comb that benefits from the reliable, low coupling loss connection between the MRR and FA, as well as a robust thermal-controlled DKS generation method. Therefore, our experiments are no longer coupling sta...

The steady DKSs in microresonators, where the cavity dispersion is balanced by Kerr nonlinearity, as well as the Kerr gain and cavity dissipation1, have attracted great interest in the scientific research community for their ultra-high repetition rate, compact size, and low cost2. In the time domain, DKSs are stable pulse trains that have been used for high-speed ranging measurement3 and molecular spectroscopy4. In the frequency domain, DKSs have a series of frequency lines with equal frequency spacing that are suitable for wavelength-division-multiplex (WDM) communications systems5,6, optical frequency synthesis7,8, and ultra-low noise microwave generation9,10, etc. The phase noise or linewidth of comb lines directly affects the performance of these application systems. It has been proven that all the comb lines have a similar linewidth with the pump11. Therefore, using an ultra-narrow linewidth laser as a pump is an effective approach to improve the performance of DKSs. However, the pumps of most reported DKSs are frequency sweeping external cavity diode lasers (ECDLs), which suffer from relatively high noise and have a broad linewidth on the order of tens to hundreds of kHz. Compared with tunable lasers, fixed-frequency lasers have less noise, narrower linewidths&#160;and smaller volume. For example, Menlo systems can provide ultra-stable laser products with a linewidth of less than 1 Hz. Using such a frequency fixed laser as a pump can significantly reduce the noise of the generated DKSs. Recently, microheater or thermoelectric cooler (TEC)-based thermal tuning methods have been used for DKSs generation12,13,14.
Repetition rate stability is another important parameter of DKSs. Generally, frequency counters are used to characterize the frequency stability of DKSs within a gate time, which is generally on the order of a microsecond to a thousand seconds15,16. Limited by the bandwidth of the photodetector and frequency counter, electro-optic modulators or reference lasers are typically used to lower the detected frequency when the free-spectral-range (FSR) of the DKSs is over 100 GHz. This not only increases the complexity of test systems, but also produces additional measurement errors caused by the stability of RF sources or reference lasers.
In this paper, a micro-ring resonator (MRR) is butterfly packaged with a commercial TEC chip that is used to control the operation temperature. Using a frequency fixed laser with a linewidth of 100 Hz as a pump, soliton crystals (SCs) are stably generated by manually decreasing the operating temperature; these are special DKSs that can completely fill a resonator with collectively ordered ensembles of copropagating solitons17. To the best of our knowledge, this is the narrowest linewidth pump in DKSs generation experiments. The power spectral density (PSD) spectrum of every comb line is measured based on a delayed self-heterodyne interferometer (DSHI) method. Benefitting from the ultra-narrow linewidth of the comb lines, the repetition rate instability of soliton crystals (SCs) is derived from the central frequency drift of the PSD curves. For the SC with a single vacancy, we obtained a repetition rate instability of ~53.24 Hz within 10 &#181;s and ~509.32 Hz within 125 &#181;s.
The protocol consists of several main stages: First, the MRR is coupled with a fiber array (FA) using a six-axis coupling stage. The MRR is fabricated by a high-index doped silica glass platform18,19. Then, the MRR is packaged into a 14-pin butterfly package, which increases the stability for the experiments. SCs are generated using a thermal-controlled method. Finally, the repetition rate fluctuations of SCs are measured by a DSHI method.

<table border="0" cellpadding="0" cellspacing="0" style="width:1421px;" width="1421">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="63">
			<td height="63" style="height:63px;width:299px;">6-axis coupling stage</td>
			<td style="width:323px;">Suruga Seiki</td>
			<td style="width:161px;">KXC620G 
			KGW060</td>
			<td style="width:639px;">Contains 3 linear motorized translation states and 3 angular motorized rotational stages. 
			Linear state: Minimum stepping: 0.05 &#956;m; Travel: 20mm; Max.speed: 25mm/s; Repeatability: +/-0.3 &#956;m; Rotational stage:Travel: &#177;8&#176;; Resolution/pulse: 0.003 degree; Repeatability:&#177;0.005&#176;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:299px;">Abrasive powder</td>
			<td style="width:323px;">Shenyang Kejing Auto-Instrument Co., LTD</td>
			<td>2980002</td>
			<td>Silicon carbide, granularity: 1.5 &#956;m</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:299px;">Glue 3410</td>
			<td style="width:323px;">Electronic Materials Incorporated</td>
			<td style="width:161px;">Optocast 3410</td>
			<td style="width:639px;">Optocast 3410 is an ultra violet light and heat curable epoxy suitable for opto-electronic assembly. It cures rapidly when exposed to U.V. light in the 320-380 nm.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:299px;">High-index doped silica glass</td>
			<td style="width:323px;">Home-made</td>
			<td style="width:161px;">-</td>
			<td style="width:639px;">The MRR is fabricated by a high index doped silica glass platform. The waveguide section is 2&#215;3 &#956;m and radius is 592.1 &#956;m, corresponding to FSR of 49 GHz.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:299px;">Pump laser</td>
			<td style="width:323px;">NKT Photonics</td>
			<td style="width:161px;">E15</td>
			<td style="width:639px;">It is a continuous wave fiber laser with linewidth of 100 Hz.</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:299px;">Ultrastable Laser</td>
			<td style="width:323px;">Menlosystems</td>
			<td style="width:161px;">ORS</td>
			<td>State-of-the-art linewidth (&#60;1Hz) and stability (&#60;2 x 10-15 Hz)</td>
		</tr>
	</tbody>
</table>

rapid repetition rate fluctuation measurement of soliton crystals in a microresonator

Temporal solitons have attracted great interest in the past decades for their behavior in a steady state, where the dispersion is balanced by the nonlinearity in a propagation Kerr medium. The development of dissipative Kerr solitons (DKSs) in high-Q microcavities drives a novel, compact, chip-scale soliton source. When DKSs serve as femtosecond pulses, the repetition rate fluctuation can be applied to ultrahigh precision metrology, high-speed optical sampling, and optical clocks, etc. In this paper, the rapid repetition rate fluctuation of soliton crystals (SCs), a special state of DKSs where particle-like solitons are tightly packed and fully occupy a resonator, is measured based on the well-known delayed self-heterodyne method. The SCs are generated using a thermal-controlled method. The pump is a frequency fixed laser with a linewidth of 100 Hz. The integral time in frequency fluctuation measurements is controlled by the length of the delay fiber. For a SC with a single vacancy, the repetition rate fluctuations are ~53.24 Hz within 10 &#181;s and ~509.32 Hz within 125 &#181;s, respectively.

Figure 3 shows the transmission power trace while a resonance thermal was tuned across the pump. There was an obvious power step that indicated the generation of SCs. The step had similar power compared with its precursor, the modulational instability comb. Therefore, the generation of SCs was not tuning speed dependent. The SCs exhibited a great variety of states, including vacancies (Schottky defects), Frenkel defects, and superstructure12,<sup class="xre...

Watch this Scientific Journal Video about Rapid Repetition Rate Fluctuation Measurement of Soliton Crystals in a Microresonator at JoVE.com

Rapid Repetition Rate Fluctuation Measurement of Soliton Crystals in a Microresonator

Here, we present a protocol to generate soliton crystals in a butterfly-packaged micro-ring resonator using a thermal tuned method. Further, the repetition rate fluctuations of a soliton crystal with a single vacancy are measured using a delayed self-heterodyne method.

Temporal solitons have attracted great interest in the past decades for their behavior in a steady state, where the dispersion is balanced by the ...

rapid-repetition-rate-fluctuation-measurement-soliton-crystals

Universidad San Sebastian

Research

Education

JoVE Journal

JoVE Core

Statistics

Engineering

Unit 1

Measure of Central Tendency

SCIENTISTS IN ACTION

3.0K Views.  Chinese Academy of Sciences (CAS). Here, we present a protocol to generate soliton crystals in a butterfly-packaged micro-ring resonator using a thermal tuned method. Further, the repetition rate fluctuations of a soliton crystal with a single vacancy are measured using a delayed self-heterodyne method.

Video: Rapid Repetition Rate Fluctuation Measurement of Soliton Crystals in a Microresonator

Ultrasound Velocity Measurement in a Liquid Metal Electrode

A growing number of electrochemical technologies depend on fluid flow, and often that fluid is opaque. Measuring the flow of an opaque fluid is inherently more difficult than measuring the flow of a transparent fluid, since optical methods are not applicable. Ultrasound can be used to measure the velocity of an opaque fluid, not only at isolated points, but at hundreds or thousands of points arrayed along lines, with good temporal resolution. When applied to a liquid metal electrode, ultrasound velocimetry involves additional challenges: high temperature, chemical activity, and electrical conductivity. Here we describe the experimental apparatus and methods that overcome these challenges and allow the measurement of flow in a liquid metal electrode, as it conducts current, at operating temperature. Temperature is regulated within &#177;2 &#176;C using a Proportional-Integral-Derivative (PID) controller that powers a custom-built furnace. Chemical activity is managed by choosing vessel materials carefully and enclosing the experimental setup in an argon-filled glovebox. Finally, unintended electrical paths are carefully prevented. An automated system logs control settings and experimental measurements, using hardware trigger signals to synchronize devices. This apparatus and these methods can produce measurements that are impossible with other techniques, and allow optimization and control of electrochemical technologies like liquid metal batteries.

Ultrasound velocimetry is used to study mixing by fluid flow in liquid metal electrodes. The focus of this manuscript is to illustrate the methods used for making precise, spatially-resolved ultrasound measurements while limiting oxidation and controlling and monitoring temperature, applied current, and the heater power being supplied.

A growing number of electrochemical technologies depend on fluid flow, and often that fluid is opaque. Measuring the flow of an opaque fluid is inherently ...

Advanced Experimental Methods for Low-temperature Magnetotransport Measurement of Novel Materials

Novel electronic materials are often produced for the first time by synthesis processes that yield bulk crystals (in contrast to single crystal thin film synthesis) for the purpose of exploratory materials research. Certain materials pose a challenge wherein the traditional bulk Hall bar device fabrication method is insufficient to produce a measureable device for sample transport measurement, principally because the single crystal size is too small to attach wire leads to the sample in a Hall bar configuration. This can be, for example, because the first batch of a new material synthesized yields very small single crystals or because flakes of samples of one to very few monolayers are desired. In order to enable rapid characterization of materials that may be carried out in parallel with improvements to their growth methodology, a method of device fabrication for very small samples has been devised to permit the characterization of novel materials as soon as a preliminary batch has been produced. A slight variation of this methodology is applicable to producing devices using exfoliated samples of two-dimensional materials such as graphene, hexagonal boron nitride (hBN), and transition metal dichalcogenides (TMDs), as well as multilayer heterostructures of such materials. Here we present detailed protocols for the experimental device fabrication of fragments and flakes of novel materials with micron-sized dimensions onto substrate and subsequent measurement in a commercial superconducting magnet, dry helium close-cycle cryostat magnetotransport system at temperatures down to 0.300 K and magnetic fields up to 12 T.

We describe the methodology of mechanical exfoliation and deposition of flakes of novel materials with micron-sized dimensions onto substrate, fabrication of experimental device structures for transport experimentation, and the magnetotransport measurement in a dry helium close-cycle cryostat at temperatures down to 0.300 K and magnetic fields up to 12 T.

Novel electronic materials are often produced for the first time by synthesis processes that yield bulk crystals (in contrast to single crystal thin film ...

Methods for Measuring the Orientation and Rotation Rate of 3D-printed Particles in Turbulence

Experimental methods are presented for measuring the rotational and translational motion of anisotropic particles in turbulent fluid flows. 3D printing technology is used to fabricate particles with slender arms connected at a common center. Shapes explored are crosses (two perpendicular rods), jacks (three perpendicular rods), triads (three rods in triangular planar symmetry), and tetrads (four arms in tetrahedral symmetry). Methods for producing on the order of 10,000 fluorescently dyed particles are described. Time-resolved measurements of their orientation and solid-body rotation rate are obtained from four synchronized videos of their motion in a turbulent flow between oscillating grids with R&#955; = 91. In this relatively low-Reynolds number flow, the advected particles are small enough that they approximate ellipsoidal tracer particles. We present results of time-resolved 3D trajectories of position and orientation of the particles as well as measurements of their rotation rates.

We use 3D printing to fabricate anisotropic particles in the shapes of jacks, crosses, tetrads, and triads, whose alignments and rotations in turbulent fluid flow can be measured from multiple simultaneous video images.

Experimental methods are presented for measuring the rotational and translational motion of anisotropic particles in turbulent fluid flows. 3D printing ...

A High Performance Impedance-based Platform for Evaporation Rate Detection

This paper describes the method of a novel impedance-based platform for the detection of the evaporation rate. The model compound hyaluronic acid was employed here for demonstration purposes. Multiple evaporation tests on the model compound as a humectant with various concentrations in solutions were conducted for comparison purposes. A conventional weight loss approach is known as the most straightforward, but time-consuming, measurement technique for evaporation rate detection. Yet, a clear disadvantage is that a large volume of sample is required and multiple sample tests cannot be conducted at the same time. For the first time in literature, an electrical impedance sensing chip is successfully applied to a real-time evaporation investigation in a time sharing, continuous and automatic manner. Moreover, as little as 0.5 ml of test samples is required in this impedance-based apparatus, and a large impedance variation is demonstrated among various dilute solutions. The proposed high-sensitivity and fast-response impedance sensing system is found to outperform a conventional weight loss approach in terms of evaporation rate detection.

This paper presents an impedance-based apparatus for evaporation rate detection of solutions. It offers clear advantages over a conventional weight loss approach: a fast response, high-sensitivity detection, a small sample requirement, multiple sample measurements, and easy disassembly for cleaning and reuse purposes.

This paper describes the method of a novel impedance-based platform for the detection of the evaporation rate. The model compound hyaluronic acid was ...

Optical Trap Loading of Dielectric Microparticles In Air

We demonstrate a method to trap a selected dielectric microparticle in air using radiation pressure from a single-beam gradient optical trap. Randomly scattered dielectric microparticles adhered to a glass substrate are momentarily detached using ultrasonic vibrations generated by a piezoelectric transducer (PZT). Then, the optical beam focused on a selected particle lifts it up to the optical trap while the vibrationally excited microparticles fall back to the substrate. A particle may be trapped at the nominal focus of the trapping beam or at a position above the focus (referred to here as the levitation position) where gravity provides the restoring force. After the measurement, the trapped particle can be placed at a desired position on the substrate in a controlled manner. 
In this protocol, an experimental procedure for selective optical trap loading in air is outlined. First, the experimental setup is briefly introduced. Second, the design and fabrication of a PZT holder and a sample enclosure are illustrated in detail. The optical trap loading of a selected microparticle is then demonstrated with step-by-step instructions including sample preparation, launching into the trap, and use of electrostatic force to excite particle motion in the trap and measure charge. Finally, we present recorded particle trajectories of Brownian and ballistic motions of a trapped microparticle in air. These trajectories can be used to measure stiffness or to verify optical alignment through time domain and frequency domain analysis. Selective trap loading enables optical tweezers to track a particle and its changes over repeated trap loadings in a reversible manner, thereby enabling studies of particle-surface interaction.

A protocol for launching and stably trapping selected dielectric microparticles in air is presented.

We demonstrate a method to trap a selected dielectric microparticle in air using radiation pressure from a single-beam gradient optical trap. Randomly ...

Measurement of Quantum Interference in a Silicon Ring Resonator Photon Source

Silicon photonic chips have the potential to realize complex integrated quantum information processing circuits, including photon sources, qubit manipulation, and integrated single-photon detectors. Here, we present the key aspects of preparing and testing a silicon photonic quantum chip with an integrated photon source and two-photon interferometer. The most important aspect of an integrated quantum circuit is minimizing loss so that all of the generated photons are detected with the highest possible fidelity. Here, we describe how to perform low-loss edge coupling by using an ultra-high numerical aperture fiber to closely match the mode of the silicon waveguides. By using an optimized fusion splicing recipe, the UHNA fiber is seamlessly interfaced with a standard single-mode fiber. This low-loss coupling allows the measurement of high-fidelity photon production in an integrated silicon ring resonator and the subsequent two-photon interference of the produced photons in a closely integrated Mach-Zehnder interferometer. This paper describes the essential procedures for the preparation and characterization of high-performance and scalable silicon quantum photonic circuits.

Silicon photonic chips have the potential to realize complex integrated quantum systems. Presented here is a method for preparing and testing a silicon photonic chip for quantum measurements.

Silicon photonic chips have the potential to realize complex integrated quantum information processing circuits, including photon sources, qubit ...

Standardized Method for Measuring Collection Efficiency from Wipe-sampling of Trace Explosives

One of the limiting steps to detecting traces of explosives at screening venues is effective collection of the sample. Wipe-sampling is the most common procedure for collecting traces of explosives, and standardized measurements of collection efficiency are needed to evaluate and optimize sampling protocols. The approach described here is designed to provide this measurement infrastructure, and controls most of the factors known to be relevant to wipe-sampling. Three critical factors (the applied force, travel distance, and travel speed) are controlled using an automated device. Test surfaces are chosen based on similarity to the screening environment, and the wipes can be made from any material considered for use in wipe-sampling. Particle samples of the explosive 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) are applied in a fixed location on the surface using a dry-transfer technique. The particle samples, recently developed to simulate residues made after handling explosives, are produced by inkjet printing of RDX solutions onto polytetrafluoroethylene (PTFE) substrates. Collection efficiency is measured by extracting collected explosive from the wipe, and then related to critical sampling factors and the selection of wipe material and test surface. These measurements are meant to guide the development of sampling protocols at screening venues, where speed and throughput are primary considerations.

Optimized sampling protocols and the development of new wipe materials can be facilitated by standardized measurements of collection efficiency from wipe-sampling. Our approach for sampling trace explosives uses an automated device to control speed, force, and distance during wipe-sampling followed by extraction of collected explosives.

One of the limiting steps to detecting traces of explosives at screening venues is effective collection of the sample. Wipe-sampling is the most common ...

Generation of Size-controlled Poly (ethylene Glycol) Diacrylate Droplets via Semi-3-Dimensional Flow Focusing Microfluidic Devices

Uniform and size-controllable poly (ethylene glycol) diacrylate (PEGDA) droplets could be produced via the flow focusing process in a microfluidic device. This paper proposes a semi-three-dimensional (semi-3D) flow-focusing microfluidic chip for droplet formation. The polydimethylsiloxane (PDMS) chip was fabricated using the multi-layer soft lithography method. Hexadecane containing surfactant was used as the continuous phase, and PEGDA with the ultraviolet (UV) photo-initiator was the dispersed phase. Surfactants allowed the local surface tension to drop and formed a more cusped tip which promoted breaking into tiny micro-droplets. As the pressure of dispersed phase was constant, the size of droplets became smaller with increasing continuous phase pressure before dispersed phase flow was broken off. As a result, droplets with size variation from 1 &#181;m to 80 &#181;m in diameter could be selectively achieved by changing the pressure ratio in two inlet channels, and the average coefficient of variation was estimated to be below 7%. Furthermore, droplets could turn into micro-beads by UV exposure for photo-polymerization. Conjugating biomolecules on such micro-beads surface have many potential applications in the fields of biology and chemistry.

Generation of Size-controlled Poly ethylene Glycol Diacrylate Droplets via Semi-3-Dimensional Flow Focusing Microfluidic Devices

Here, we present a protocol to illustrate the fabrication processes and verifying experiments of a semi-three-dimensional (semi-3D) flow-focusing microfluidic chip for droplet formation.

Uniform and size-controllable poly (ethylene glycol) diacrylate (PEGDA) droplets could be produced via the flow focusing process in a microfluidic device. ...

Measuring Magnetically-Tuned Ferroelectric Polarization in Liquid Crystals

Materials showing coupling phenomena between magnetism and (ferro)electricity, i.e., magnetoelectric effects, have attracted a great deal of attention due to their potential applications for future device technologies such as sensors and storage. However, conventional approaches, which usually utilize materials containing magnetic metal ions (or radicals), have a major problem: only a few materials have been found to show the coupling phenomena at room temperature. Recently, we proposed a new approach to achieve room-temperature magnetoelectrics. In contrast to conventional approaches, our alternative proposal focuses on a completely different material, a &#34;liquid crystal&#34;, free from magnetic metal ions. In such liquid crystals, a magnetic field can be utilized to control the orientational state of constituent molecules and the corresponding electric polarization through magnetic anisotropy of the molecules; it is an unprecedented mechanism of the magnetoelectric effect. In this context, this paper provides a protocol to measure ferroelectric properties induced by a magnetic field, that is, the direct magnetoelectric effect, in a liquid crystal. With the method detailed here, we successfully detected magnetically-tuned electric polarization in the chiral smectic C phase of a liquid crystal at room temperature. Taken together with the flexibility of constituent molecules, which directly affects the magnetoelectric responses, the introduced method will serve to allow liquid crystal cells to acquire more functions as room-temperature magnetoelectrics and associated optical materials.

In this report, we present a protocol to examine direct magnetoelectric effects, i.e., induction of ferroelectric polarization by applying magnetic fields, in liquid crystals. This protocol provides a unique approach, supported by the softness of liquid crystals, to achieve room-temperature magnetoelectrics.

Materials showing coupling phenomena between magnetism and (ferro)electricity, i.e., magnetoelectric effects, have attracted a great deal of attention due ...

A Rapid Method for Modeling a Variable Cycle Engine

The variable cycle engines (VCE) that combine the advantages of turbofan and turbojet engines, are widely considered to be the next generation aircraft engines. However, developing VCE requires high costs. Thus, it is essential to build a mathematical model when developing an aircraft engine, which may avoid a large number of real tests and reduce the cost dramatically. Modeling is also crucial in control law development. In this article, based on a graphical simulation environment, a rapid method for modeling a double bypass variable cycle engine using object-oriented modeling technology and modular hierarchical architecture is described. Firstly, the mathematical model of each component is built based on the thermodynamic calculation. Then, a hierarchical engine model is built via the combination of each component mathematical model and the N-R solver module. Finally, the static and dynamic simulations are carried out in the model and the simulation results prove the effectiveness of the modeling method. The VCE model built through this method has the advantages of clear structure and real-time observation.

Here, we present a protocol to build a component-level mathematical model for a variable cycle engine.

The variable cycle engines (VCE) that combine the advantages of turbofan and turbojet engines, are widely considered to be the next generation aircraft ...