Aimin Xing

Fabrication of InP-based two-dimensional photonic crystal membrane

The fabrication process of a InP-based two-dimensional photonic crystal membrane structure is developed. The process includes a well-calibrated electron-beam (e-beam) lithography and InGaAsP/InP etching using methane–hydrogen–argon reactive ion etching. The photonic crystal blocks with ten rows of a hexagonal array of holes with various lattice constants and filling factors are successfully fabricated and characterized by optical transmission measurement. The sensitivity of the band gap to the systematic fabrication error is determined.

Detailed characterization of slow and dispersive propagation near a mini-stop-band of an InP photonic crystal waveguide.

An experimental study of light propagation near a small band gap for a lattice-of-holes InP photonic crystal waveguide is reported. Polarization-resolved measurements of power transmission, reflection and group delay clearly reveal the PC waveguide filtering properties. Group delay enhancement was observed close to the band-edges together with very large dispersion. The test devices were fabricated with a novel technique that allows incorporation of deeply-etched photonic crystals within an InP photonic integrated circuit.

Broadband Notch Filters Based on Quasi-2-D Photonic Crystal Waveguides for InP-Based Monolithic Photonic-Integrated Circuits

Asymmetric (type B) multimode photonic crystal line-defect waveguides with varying channel widths have been fabricated and analyzed experimentally. The waveguide channel widths influence the frequencies, bandwidths, and extinction of the resulting stopbands. Transmission stopbands were obtained with bandwidths greater than 20 nm and extinction equal to 20 dB. A scheme for reducing the distributed-feedback reflections from the waveguides was also devised, and a suppression of at least 10 dB was achieved. These waveguides show good prospects for the realization of very compact broadband notch filters for monolithic photonic-integrated circuits

Compact broadband photonic crystal filters with reduced back-reflections for monolithic InP-based photonic integrated circuits

A photonic crystal grating filter with an extremely wide rejection band and reduced modal back-reflections is proposed and demonstrated with a stopband extinction of 20 dB and insertion loss of less than 5 dB. The reflection-mitigation technique is shown to provide 10-15-dB reduction in reflected power. Guidelines for performance improvement are presented

Transmission measurement of tapered single-line defect photonic crystal waveguides

Two-dimensional tapered single-line defect photonic crystal (PC) waveguides were fabricated with coupled ridge waveguides in InP-InGaAsP and optical transmission characteristics measured. Three different taper designs that optimized both mode size match and impedance match between the accessing ridge waveguides and the PC waveguides were fabricated and characterized. An /spl sim/8-dB improvement of coupling efficiency was observed for the tapered structures over untapered.

Pulse compression in line defect photonic crystal waveguide

The dispersion properties of a membrane-type line-defect photonic crystal waveguide were investigated using short optical pulses. Group velocity dispersion larger than 10 ps/(mm/spl times/nm) were measured and pulse compression of approximately 60% was demonstrated.

Transmission measurement of tapered single line defect photonic crystal waveguide

Two-dimensional single-line defect Photonic Crystal (PC) waveguides were fabricated and characterized by optical transmission measurements. Different PC-waveguide tapers were investigated for coupling to access ridge waveguides; ~10-dB coupling efficiency enhancement was observed over un-tapered waveguides

Broadband photonic crystal passive filters for integrated InP photonic integrated circuits

Two broadband, InP photonic crystal optical filters with reduced back-reflections are demonstrated: one 10/spl mu/m-long low-pass with 20 dB stop-band extinction; one 30 /spl mu/m-long, 40-nm bandwidth notch with 20 dB extinction. Both could find applications as band-rejection filters in monolithic InP photonic integrated circuits.

Perspectives on the application of InP-based photonic crystal waveguides for optical signal processing

Photonic crystal waveguides have long attracted much attention in the integrated photonics community due to their high confinement properties and potential for the achievement of photonic circuits with a very high level of integration. While high propagation losses still impair most of the practical applications of such waveguides, predicted and demonstrated slow and dispersive propagation within compact lengths remain very attractive for optical signal processing. In this talk, results will be presented from an investigation on slow and dispersive propagation in two different types of InP-based photonic crystal waveguides fabricated at UCSB. Waveguides of the membrane type, with very strong vertical confinement, were fabricated and characterized, as well as guides with weak vertical confinement and deeply-etched holes. Those of the latter kind were successfully integrated with structures found in standard photonic circuits produced in our group. Detailed measurements of transmission will be presented showing slow and dispersive propagation close to band edges. Reasonable group delay enhancement is found, which is clearly dependent on propagation losses; on the other hand, extremely large GVD is found over reasonably wide bandwidths, even when considerable losses are present. This suggests that, by proper tuning of coupling coefficients, very compact dispersion-compensating elements can be designed. A discussion on the advantages and disadvantages, as well as different possibilities of using this class of waveguides for the implementation of delay lines and dispersion compensation will be presented.

InP photonic crystal membrane structures: Fabrication accuracy and optical performance

Two-dimensional photonic crystal membranes with coupled ridge waveguides were fabricated in InP∕InGaAsP by using e-beam lithography and reactive ion etching. The optical transmission characteristics were measured and a photonic band gap with better than 20dB extinction ratio was observed. The band-gap dependence on radius-to-lattice constant ratio (r∕a) was numerically and experimentally investigated. Predictable, accurate placement of the band edge by varying r∕a is demonstrated.