Optical spotsize converter using narrow laterally tapered waveguide for planar lightwave circuits

We present a full description of the design and fabrication of a compact laterally tapered spotsize converter (SSC) that provides both low-loss coupling and large fabrication tolerances. The SSC is based on a laterally tapered waveguide with a narrow core width that can be fabricated simply by using the usual fabrication process. We discuss the design concept of the SSC in detail and provide a simple design procedure with which to obtain the optimum SSC design parameters. We also investigate the fiber misalignment tolerance and mode field diameter of the SSC and confirm that it is suitable for integration with large-scale optical devices. Furthermore, we examine the performance of the SSC for higher refractive index difference (/spl Delta/) of 2.0% and 2.5% with a smaller bending radius. We fabricated the 2-mm-long SSC using 1.5%-, 2.0%-, and 2.5%-/spl Delta/ silica-based planar lightwave circuits. This enabled us to reduce the single-mode fiber coupling loss to 0.4 dB at a single waveguide junction with a low polarization-dependent loss of 0.05 dB regardless of the /spl Delta/ values, while providing a core width fabrication tolerance of /spl plusmn/0.3 /spl mu/m, and an endface position tolerance of /spl plusmn/0.2 mm.

[1]  B. Offrein,et al.  A very short planar silica spot-size converter using a nonperiodic segmented waveguide , 1998 .

[2]  M. Itoh,et al.  Low-loss fibre-pigtailed 256 channel arrayed-waveguide grating multiplexer using cascaded laterally-tapered waveguides , 2001 .

[3]  K. Okamoto.  Fundamentals of Optical Waveguides , 2000 .

[4]  Hideki Fukano,et al.  Optical spot-size converters for low-loss coupling between fibers and optoelectronic semiconductor devices , 1996 .

[5]  Tsutomu Kitoh,et al.  400-channel arrayed-waveguide grating with 25 GHz spacing using 1.5%-Δ waveguides on 6-inch Si wafer , 2001 .

[6]  T. Shimizu,et al.  Index-and-dimensional taper and its application to photonic devices , 1992 .

[7]  Ingrid Moerman,et al.  A review on fabrication technologies for the monolithic integration of tapers with III-V semiconductor devices , 1997 .

[8]  Y. Hibino.  High contrast waveguide devices , 2001, OFC 2001. Optical Fiber Communication Conference and Exhibit. Technical Digest Postconference Edition (IEEE Cat. 01CH37171).

[9]  O. Mitomi,et al.  A simple laterally tapered waveguide for low-loss coupling to single-mode fibers , 1993, IEEE Photonics Technology Letters.

[10]  M. Itoh,et al.  Birefringence compensated silica-based waveguide with undercladding ridge , 2002 .

[11]  Yasuo Kokubun,et al.  Low-loss spot-size transformer by dual tapered waveguides (DTW-SST) , 1990 .

[12]  T. Miya,et al.  Silica-based planar lightwave circuits , 1998 .

[13]  K. Okamoto,et al.  Very low insertion loss arrayed-waveguide grating with vertically tapered waveguides , 2000, IEEE Photonics Technology Letters.

[14]  J. C. Chen,et al.  Computation of higher-order waveguide modes by imaginary-distance beam propagation method , 1994 .

[15]  Amos A. Hardy,et al.  Modes of periodically segmented waveguides , 1993 .

[16]  Mikitaka Itoh,et al.  Large reduction of singlemode-fibre coupling loss in 1.5% /spl Delta/ planar lightwave circuits using spot-size converters , 2002 .

[17]  Tsutomu Kitoh,et al.  Low-loss 1.5%-Δ arrayed waveguide grating with narrow laterally tapered spotsize converter , 2001 .

[18]  W. Weiershausen,et al.  Laterally tapered InP-InGaAsP waveguides for low-loss chip-to-fiber butt coupling: a comparison of different configurations , 1995, IEEE Photonics Technology Letters.

[19]  T. Saida,et al.  Compact and low-loss arrayed waveguide grating module with tolerance-relaxed spot-size converter , 2003, IEEE Photonics Technology Letters.

[20]  M. Ishii,et al.  Packaging and environmental stability of thermally controlled arrayed-waveguide grating multiplexer module with thermoelectric device , 1998 .