Maria V. Kotlyar

Self-collimating photonic crystal polarization beam splitter

We present theoretical and experimental results of a polarization splitter device that consists of a photonic crystal (PhC) slab, which exhibits a large reflection coefficient for TE and a high transmission coefficient for TM polarization. The slab is embedded in a PhC tile operating in the self-collimation mode. Embedding the polarization-discriminating slab in a PhC with identical lattice symmetry suppresses the in-plane diffraction losses at the PhC-non-PhC interface. The optimization of the PhC-non-PhC interface is thereby decoupled from the optimization of the polarizing function. Transmissions as high as 35% for TM- and 30% for TE-polarized light are reported.

Low-loss photonic crystal defect waveguides in InP

We have fabricated high-quality planar photonic crystal defect waveguides in InP/InGaAsP material. Using Fourier analysis of the Fabry-Perot fringes obtained in transmission, we derive the propagation losses. Values as small as 1.8 dB/mm for waveguides consisting of three rows of missing holes (W3) were measured. We believe that the reduction in losses is due to the high quality of etching carried out using a high beam voltage–current ratio regime of chemically assisted ion-beam etching.

Compact polarization converter in InP-based material

We present a polarization converter using one-dimensional grating principles. The device is based on slanted slots etched deeply into an InP/InGaAsP heterostructure. Almost complete polarization conversion, with a 14 dB extinction ratio, is observed for a device less than 2 microm long.

High-aspect-ratio chemically assisted ion-beam etching for photonic crystals using a high beam voltage-current ratio

We investigate etching conditions for photonic crystals (PhCs) in InGaAsP/InP and AlGaAs/GaAs using a new regime of CAIBE operation. We show that the beam voltage-current ratio is critical in obtaining high material/mask selectivity. For one-dimensional PhCs, i.e., air slots, selectivities of 22:1 and 50:1 were achieved in InP and GaAs, respectively, using a very high beam voltage (about 1500 V) and a low beam current (about 10 mA). Etched features were observed to be very smooth, i.e., edge roughness was low. Two-dimensional PhCs were etched in InGaAsP/InP under similar conditions achieving selectivities up to 27:1 and 34:1 for hole diameters of 170 and 270 nm, respectively.

Photonic crystal lens for coupling two waveguides

We report the design, fabrication, and characterization of a new nanophotonic device comprising a two-dimensional photonic crystal (PhC) lens of size 3x4 microm fabricated in silicon-on-insulator. The PhC lens is put at the output of a planar waveguide of width 4.5 microm to couple light into a planar waveguide of width 1 microm, with two waveguides being of length 5 mm. A 1 microm off-axis displacement of the smaller waveguide leads to an 8-fold reduction of output light intensity, which means that the focal spot size at output of the PhC lens in silicon is less than 1 microm. The simulation has shown that the PhC lens has maximal transmittance at 1.55 microm, with the coupling efficiency being 73%. The focal spot size of the lens in air calculated at the FWHM is 0.32lambda (where lambda is the wavelength).

Reduced surface sidewall recombination and diffusion in quantum-dot lasers

We examine the surface recombination rate in quantum-dot semiconductor lasers and determine the diffusion length (1.0 mum) and, for the first time, provide a value for surface recombination velocity (5times104 cm/s) in quantum-dot material. As a result of strong carrier confinement in the dots, these values are much lower than in comparable quantum-well lasers (5times105 cm/s and 5 mum, respectively) allowing the creation of narrow (2-3 mum wide) lasers with comparable threshold currents to those of broad area devices

Fabrication of photonic crystals using a spin-coated hydrogen silsesquioxane hard maska)

We present a method for creating a hard mask for the dry etching of microphotonic structures and devices. We demonstrate that spin-on glass [hydrogen silsesquioxane (HSQ)] has sufficient dry etch resistance to allow the creation of high-quality, deeply etched photonic crystals. Furthermore, HSQ is a more favorable hard mask for the creation of active devices than plasma-enhanced chemical-vapor deposition (PECVD) silica, as less damage is incurred. It is also an economic and convenient replacement for PEVCD in photonic crystal fabrication. We examine this method and show that it can create photonic crystals of equivalent quality to those created using PEVCD masking.

Compact Slanted Grating Couplers Between Optical Fiber and InP–InGaAsP Waveguides

We present theoretical and experimental results for compact slanted gratings for vertical coupling between single-mode fiber and InP-InGaAsP waveguides. The maximum calculated coupling efficiency is 59%. We have measured a coupling efficiency of 16% for a 10-mum-long slanted grating

Electrooptic tuning of InP-based microphotonic Fabry-Perot filters

This paper presents the experimental results for compact (20- and 40-/spl mu/m-long) electrooptically tuned deeply etched Fabry-Perot (F-P) filters in InP-based material. Both the quantum-confined Stark effect (QCSE) and carrier-injection (C-I) effects were implemented to achieve tunability of these microcavity filters. Red and blue shifts of the transmission peaks in the order of 1 to 2 nm were observed for both effects, and the limitations on C-I due to thermal effect are clearly demonstrated and discussed. The advantages and disadvantages of both tuning mechanisms are highlighted.

Electrically tunable multiquantum-well InGaAsP-InGaAsP microphotonic filter

Planar waveguide-based Fabry-Pe/spl acute/rot microcavities of 20- and 40-/spl mu/m length have been studied. The cavity resonance has been tuned via carrier injection by a maximum of 1.9 nm at a wavelength of 1.3 /spl mu/m with only 6 mW of tuning power. The interplay between electrical and thermal tuning is highlighted.