Optical spot-size converters for low-loss coupling between fibers and optoelectronic semiconductor devices

Structures of spot size converters that allow low loss and easy coupling between an optical semiconductor device and a fiber are proposed and designed theoretically. These spot-size converters have a tapered small core for expanding the mode field. They also have a double cladding region which consists of an n/sup +/-doped InP substrate as the outer cladding and a p-doped or nondoped InP layer as the inner cladding with a ridge structure. This double cladding utilizes the plasma effect of a carrier which makes the refractive index of highly doped n-InP lower than that of p-doped or nondoped InP. The double-cladding structure can tightly confine an expanded mode field in the inner cladding, and results in low radiation loss at the tapered waveguide, in addition, this structure reforms the mode field shape into a Gaussian-like shape and achieves a low loss coupling of less than 1 dB with a large misalignment tolerance for fiber coupling. These spot-size converters are easily fabricated and applicable to all types of optical semiconductor devices.

[1]  M. J. Robertson,et al.  1.56μm InGaAsP/InP tapered active layer multiquantum well laser with improved coupling to cleaved singlemode fibre , 1994 .

[2]  U. Koren,et al.  Tapered waveguide InGaAs/InGaAsP multiple-quantum-well lasers , 1990, IEEE Photonics Technology Letters.

[3]  Y. Tohmori,et al.  1.3 /spl mu/m large spot-size laser diodes with laterally tapered active layer , 1995 .

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

[6]  P. Doussiere,et al.  Tapered active stripe for 1.5‐μm InGaAsP/InP strained multiple quantum well lasers with reduced beam divergence , 1994 .

[7]  O. Mitomi,et al.  Design of a single-mode tapered waveguide for low-loss chip-to-fiber coupling , 1994 .

[8]  H. Melchior,et al.  Vertically tapered InGaAsP/InP waveguides for highly efficient coupling to flat‐end single‐mode fibers , 1994 .

[9]  A. Carenco,et al.  Quasi planar spot-size transformer for efficient coupling between a cleaved fibre and an InP/InGaAsP rib waveguide , 1994, IEEE Photonics Technology Letters.

[10]  Y. Tohmori,et al.  High temperature operation with low-loss coupling to fibre for narrow-beam 1.3 μm lasers with butt-jointed selective grown spot-size converter , 1995 .

[11]  Hideki Fukano,et al.  Spot-size converted 1.3 µm laser with butt-jointed selectively grown vertically tapered waveguide , 1995 .

[12]  S. Sawa,et al.  Analysis of tapered optical slab waveguides with hypothetical boundaries , 1980 .

[13]  R. C. Kistler,et al.  Efficient coupling of a semiconductor laser to an optical fiber by means of a tapered waveguide on silicon , 1989 .

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

[15]  Mitsuru Ekawa,et al.  Tapered thickness MQW waveguide BH MQW lasers , 1994, IEEE Photonics Technology Letters.

[16]  W. D. Goodhue,et al.  Reduced-confinement GaAlAs tapered waveguide antennas for enhanced far-field beam directionality , 1991 .

[17]  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.

[18]  Yasuhiro Kondo,et al.  Monolithically integrated DBR lasers with simple tapered waveguide for low-loss fibre coupling , 1993 .

[19]  Yuichi Tohmori,et al.  Dynamic characteristics of a 1.3 μm laser diode integrated with a spot-size converter coupled to a silica planar lightwave circuit , 1995 .

[20]  E Kapon,et al.  Two-dimensional control of mode size in optical channel waveguides by lateral channel tapering. , 1991, Optics letters.