Alexander kellarev
Tel Aviv University
Alexander Kellarev has obtained his BSC and MSC degrees in Physics from Technion Institute (Israel). Since 2014 he is working on PHD studies in Tel Aviv University under supervision of Prof. Shlomo Ruschin at the faculty of Engineering, department of Physical Electronics. His professional experience includes spectrometric and radiometric measurements and imaging in visible, infrared and terahertz spectral regions, design and construction of optical systems, theoretical modelling, data analysis and image processing.
Introduction Currently creation of waveguides and other planar optical elements is performed using relatively sophisticated methods, which involve complex apparatus,and often requires making multiple lithography masks and... [ view full abstract ]
Introduction
Currently creation of waveguides and other planar optical elements is performed using relatively sophisticated methods, which involve complex apparatus,and often requires making multiple lithography masks and growing of additional structure layers. An alternative method of creation of such elements is patterning in a porous substrate by pore filling. [1] This process is relatively simple and can be used to create regions with desired refractive index when applied with a mask or other patterning techniques. Porous silicon (PSi) is an optical metamaterial, which possesses a high ability to absorb other substances. PSi with specific refractive index can be created by means of electrochemical etching of Si wafer.
Methods
To create the light-guiding structures we used an oxidised Si wafer with two porous layers of different refractive indices, where the bottom layer serves as cladding. KDP salt solution was applied to fill the pores by two methods: printing and through a photoresist mask. After the pore filling the wafer was cleaved to allow access to the sides of the layers.
Propagation was examined at wavelengths 1.064μm and 1.550μm. Laser light was inserted into the waveguides using a lensed fiber. Transmitted light and light scattered from the top surface were acquired by means of imaging. The acquired images were used to analyse the spatial distribution of the transmitted light and to estimate the propagation loss.
Results
We created straight waveguides, tapered waveguides, waveguides with S-bends and Y-splitters by means of the method described above. As an example, part of the top surface is presented in Figure 1, showing a waveguide and a Y-splitter. We successfully measured light propagation through all the created structures. Examples of the acquired images are presented in Figure 2. At λ=1.064μm we obtained multimode propagation for waveguides designed with 30-micron width while waveguides designed with 3-micron width support 2 propagated modes.
Preliminary best measured losses were around 3.4dB/cm (λ=1.064μm) and 0.2dB/cm (λ=1.550μm).
Discussion
We demonstrated the possibility of creation of optical elements in PSi by pore filling. The measured losses are competitive to recently published reports for patterned waveguides in PSi.
[1] Optical Materials, vol.85, 2018, pp.113-120
