Design and Fabrication of an Optical Fiber Made of Water

Summary

This protocol describes the design and manufacture of a water bridge and its activation as a water fiber. The experiment demonstrates that capillary resonances of the water fiber modulate its optical transmission.

Abstract

In this report, an optical fiber of which the core is made solely of water, while the cladding is air, is designed and manufactured. In contrast with solid-cladding devices, capillary oscillations are not restricted, allowing the fiber walls to move and vibrate. The fiber is constructed by a high direct current (DC) voltage of several thousand volts (kV) between two water reservoirs that creates a floating water thread, known as a water bridge. Through the choice of micropipettes, it is possible to control the maximal diameter and length of the fiber. Optical fiber couplers, at both sides of the bridge, activate it as an optical waveguide, allowing researchers to monitor the water fiber capillary body waves through transmission modulation and, therefore, deducing changes in surface tension.

Co-confining two important wave types, capillary and electromagnetic, opens a new path of research in the interactions between light and liquid-wall devices. Water-walled microdevices are a million times softer than their solid counterparts, accordingly improving the response to minute forces.

Introduction

Since the breakthrough of optical fibers in communication, awarded with a Nobel prize in 2009¹, a series of fiber-based applications grew alongside. Nowadays, fibers are a necessity in laser surgeries², as well as in coherent X-ray generation^3,4, guided-sound⁵ and supercontinuum⁶. Naturally, the research on fiber optics expanded from utilizing solids into exploiting liquids for optical wave guiding, where liquid-filled microchannels and laminar flow combine the transportation properties of a liquid with the advantag....

Protocol

CAUTION: This experiment involves high voltage. It is the reader's responsibility to verify with the safety authorities that their experiment follows regulations before turning on the high voltage.

NOTE: Any kind of polar liquid can be utilized to produce liquid fibers, such as ethanol, methanol, acetone, or water. The polarity of the liquid dictates the stability and diameter of the created fiber^23,24. For best results, use deionized water with 18 MΩ resistance. Before choosing optical components, such as optical fibers and light sources, consult the literature to ensure ....

Results

The coupling efficiency from a water fiber to a highly multimode fiber can be as high as 54%^25,26. The coupling efficiency to a single-mode fiber is up to 12%^25,26. Water fibers can be as thin as 1.6 µm in diameter and can have a length of 46 µm (Figure 3)^25,26, or they can b.......

Discussion

To conclude, the major advantage and uniqueness of this technique is creating a fiber which hosts three different kinds of waves: capillary, acoustic, and optical. All three waves oscillate in different regimes, opening the possibility for multi-wave detectors. As an example, airborne nanoparticles affect the surface tension of liquids. Already at the current stage, it is possible to monitor changes in the surface tension through variations in the capillary eigenfrequency. Additionally, water-walled devices are a million.......

Materials

Name	Company	Catalog Number	Comments
Deioniyzed Water			18MOhm resistance
Micropipettes, Borosilicate Glass, round, inner diameter 850 micron	Produstrial.com	#133260
Micropipettes, Borosilicate Glass, round, inner diameter 150 micron	Produstrial.com	#133258
High voltage, low current source, 3kV with 5 mA.	Bertan	Model 215
High voltage, low current source,  8 kV with 0.25 mA.	Home build
Optical fiber	Corning	HI 780 C	5 meter
Optical fiber	Thorlabs	FTO 30	5 meter
Optical fiber	Thorlabs	FTO 30	5 meter
Fiber coupled laser	FIS	SMF 28E
Photoreceiver	New Port/ New Focus	1801-FS	with fiber connection
Oscilloscope	Agilent Technologies	DSO-X 3034A
2 Degree of freedom tilt stagestage	New Port/ New Focus	M-562F-TILT
3Degree of freedom linear micro translation stage	New Port/ New Focus	M-562F-XYZ
A set of magnets
Objective 5X	Mitutoyo	MY5X-802
Objective 20 x	Mitutoyo	MY20X-804
Zoom	Navitar	12x Zoom
Microscope tube	Navitar	1-6015 standard tube
Isopropanol	Sigma Aldrich	67-63-0	Spec Grad
2 x Bare Fiber holder	Thorlabs	T711-250
2 x Translational Stage	Thorlabs	DT12
Block of PMMA for fabricating the water reservoir and pipette holder			150 x 60 x 10 mm
PTFE-Tape	Gufero	240453
Fiber coupled, cw Laser Light Source	New Port/ New Focus	TLB-6712	765-781 nm