762 IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 12, NO. 7, JULY 2000 Design of Sampled Grating DBR Lasers with Integrated Semiconductor Optical Amplifiers Beck Mason, Jonathon Barton, Greg A. Fish, Larry A. Coldren, Fellow, IEEE, and Steven P. DenBaars Abstract—High output powers and wide range quasicontinuous tuning have been achieved in a sampled-grating distributed Bragg reflector laser with an integrated semiconductor-optical-amplifier. Using an amplifier with a curved passive output waveguide to sup- press back reflection, we have achieved a quasicontinuous tuning range of over 50 nm and peak output powers greater than dBm. Optimizing the device structure and the sampled-grating mirror design has enabled tuning ranges of up to 72 nm in devices without amplifiers. Index Terms—Distributed Bragg reflector lasers, indium phos- phide, quantum well lasers, semiconductor optical amplifiers, tun- able lasers, waveguide lasers. I. INTRODUCTION W IDELY TUNABLE sampled-grating distributed Bragg reflector lasers (SGDBR) have been demonstrated with quasicontinuous tuning ranges between 30 and 60 nm [1]–[4]. These lasers have great promise as low-cost high-per- formance wavelength-agile sources for use in current and next generation dense wavelength-division-multiplexed (DWDM) fiber-optic networks. Existing applications include the re- placement of many different wavelength DFB lasers with a single tunable laser. Future applications may include use in wavelength-routing and switching architectures. In some cases, output powers as high as 10 mW are desired, however, this may be difficult to achieve simultaneously with wide tunability ( nm). A significant advantage of the sampled-grating DBR over other widely-tunable lasers is that it can be monolithically integrated with different devices such as semiconductor-op- tical-amplifiers (SOA’s) [6] and electroabsorption modulators [2] to create photonic integrated circuits with more functionality without significantly increasing the fabrication complexity. In this work, we examine the characteristics of a SGDBR with an integrated SOA. A schematic of the device is shown in Fig. 1. II. DEVICE DESIGN The device is based on a buried-ridge stripe SGDBR design with a single p-type InP regrowth [2]. The layer structure con- sists of a 350 nm thick 1.4Q waveguide layer with a six com- pressively strained % quantum-well active region grown Manuscript received October 22, 1999; revised February 9, 2000. This work was supported by the Navel research laboratory (NRL) under Grant N00014-96-1-6014. B. Mason and G. A. Fish are with Agility Communications, Inc., Santa Bar- bara, CA 93111 USA. J. Barton, L. A. Coldren, and S. P. DenBaars are with the Electrical and Com- putrer Engineering Department, University of California Santa Barbara, Santa Barbara, CA 93106 USA. Publisher Item Identifier S 1041-1135(00)05588-9. Fig. 1. SGDBR laser with integrated amplifier. on top separated by a thin InP stop-etch layer. Passive sections are formed by selectively etching off the quantum wells and regrowing an InP cap. The sampled gratings are defined holo- graphically and etched directly into the top of the waveguide layer. Lateral carrier confinement is achieved by dry etching through the waveguide layer and regrowing p-type InP over the ridge. For the lasers with integrated amplifiers, the front mirrors contain ten 58- m sampling periods with 6 m grating bursts, and the back mirrors have twelve 64 m periods with the same burst length. This gives the devices a maximum tuning range of 54 nm. The tuning enhancement factor, which is the ratio of wavelength tuning to actual mirror index tuning, for this device is 10. More details of the device structure are available in [2]. For even wider tuning ranges, a device was designed with a front mirror sampling period of 43 m and a back mirror sampling period of 46 m providing mirror peak spacings of 7.5 and 7 nm, respectively. This device had 3- m grating bursts and a de- signed tuning range of 90 nm. A semiconductor optical amplifier was integrated on chip with the 54-nm tunable laser. The amplifier had a 600- m-long active section followed by a passive section which contained a curved portion to angle the waveguide at the facet and a flared portion to expand the optical mode. The principle advantage of the integrated SOA is that it can be used to compensate for in- creased absorption loss in the mirrors at high tuning currents and increase the output power from the device. For fixed laser gain current, the output power can vary 6 dB over the tuning range. This may be compensated by increasing the laser gain as the SGDBR is tuned toward the edges of its range. However, placing the optical power control outside of the laser cavity is highly advantageous since it decouples the output power from the wavelength tuning characteristics. Nevertheless, the com- plex nature of the tuning mechanism and the tight wavelength tolerances of present DWDM networks ( 5 GHz) still requires 1041–1135/00$10.00 © 2000 IEEE