Integrated AlGaInAs-silicon evanescent race track laser and photodetector

Abstract

Recently, AlGaInAs-silicon evanescent lasers have been demonstrated as a method of integrating active photonic devices on a silicon based platform. This hybrid waveguide architecture consists of III-V quantum wells bonded to silicon waveguides. The self aligned optical mode leads to a bonding process that is manufacturable in high volumes. Here give an overview of a racetrack resonator laser integrated with two photo-detectors on the hybrid AlGaInAs-silicon evanescent device platform. Unlike previous demonstrations of hybrid AlGaInAs-silicon evanescent lasers, we demonstrate an on-chip racetrack resonator laser that does not rely on facet polishing and dicing in order to define the laser cavity. The laser runs continuous-wave (c.w.) at 1590 nm with a threshold of 175 mA, has a maximum total output power of 29 mW and a maximum operating temperature of 60 C. The output of this laser light is directly coupled into a pair of on chip hybrid AlGaInAs-silicon evanescent photodetectors used to measure the laser output.Keywords: Silicon evanescent laser, Silicon photonics, integration, photodetector, semiconductor laser IntroductionSilicon photonics has received a lot of attention by researchers with the hopes to leverage the low cost manufacturing infrastructure of CMOS photonics for applications such as chip to chip and board to board interconnects [1][2][3][4]. This work has been focused on the building blocks of photonic communication systems such as lasers [5][6][7][8], modulators, photodetectors, and others [9][10][11][12][13][14][15]. Our work has been focused on developing a hybrid integration platform that allows for III-V material functionality, such as light amplification and detection, to be utilized on silicon waveguide based devices. This platform consists of a III-V epitaxial structure bonded to a silicon waveguide to make a hybrid waveguide such that its optical mode lies primarily in the silicon region with a small portion of the mode overlapping the quantum wells of the III-V structure for optical gain. The optical mode characteristics are predominately defined by the silicon waveguide processing. Bonding can be performed without critical alignment. The remaining critical alignment steps, such as the definition of electrical current injection channels, utilize standard lithographic techniques leading to a high volume, low cost, solution for active devices on silicon. The first hybrid laser demonstration relied on the dicing and polishing of straight hybrid waveguides to define a Fabry-Perot laser cavity [16]. Here we review a monolithic hybrid AlGaInAs silicon evanescent laser based on a racetrack-resonator-topography. The laser runs continuous-wave (c.w.) with a threshold of 175 mA, a maximum total output power of 29 mW and maximum operating temperature of 60 oC. Moreover we report the integration of this laser with a hybrid AlGaInAs-silicon evanescent photodetector used to measure the laser output [17].

Light emission and enhanced nonlinearity in nanophotonic waveguide circuits by III–V/silicon-on-insulator heterogeneous integration

“…5͒ or germanium 6 for light detection and III-V material for light emission and amplification. 7,8 The high refractive index contrast between the silicon waveguide core ͑n = 3.45 at 1.55 m͒ and the SiO 2 cladding layer ͑n = 1.45 at 1.55 m͒ is ultimately exploited by using nanophotonic strip waveguides, which are defined by completely etching through a / 2n thick silicon waveguide layer. 1 This results in a single mode waveguide with cross-sectional dimensions on the order of 500ϫ 200 nm 2 ͑for operation at the 1.55 m telecommunication wavelength͒ with a very high omnidirectional refractive index contrast, which allows making wavelength-scale optical functions.…”

“…9 Recently, the work of Intel/UCSB has received a lot of attention, in which a III-V epitaxial layer is transferred onto a SOI rib waveguide structure. 8,10 While integrated optoelectronic devices were realized this way, the use of SOI rib waveguide structures limits the further downscaling of the size of the photonic integrated circuit due to the limited refractive index contrast that can be realized in this single mode rib waveguide structure. In this paper we present for the first time the realization of light emission from ultracompact III-V/SOI cavities based on the nanophotonic strip waveguide platform, resulting in devices with a typical footprint of 100 m 2 .…”

Device engineering for silicon photonics

“…Effi cient light signal detection, as a key process for communications, is thus diffi cult using silicon. Following an approach similar to that used for silicon hybrid integrated lasers based on the wafer bonding of group-III/V materials on top of patterned SOI wafers, silicon waveguides with group-III/V capping materials have been demonstrated as evanescent-fi eld detectors by various groups [33,34]. Th e 30 μm-long hybrid waveguide evanescent-fi eld detector developed by Brouckaert et al [34] has a response of was 1.0 A W -1 at a wavelength of 1,550 nm with dark current of 4.5 nA and bias voltage of 5 V. Although the performance of such hybrid photodetectors is satisfactory, the wafer bonding process is not CMOS-compatible.…”

Hybrid silicon integration

“…Fabry-Perot lasers at 1326 nm [7] and 1577 nm [8] have been fabricated using this hybrid waveguide architecture as well as optical amplifiers [9], photodetectors [10] and ring lasers [11]. The generic device process flow is as follows.…”

“…After bonding the InP is patterned into mesa's; the N-and P-metals are deposited followed by proton implantation of the mesa to form a conductive channel in the center of the mesa through which current can flow. A typical hybrid silicon active cross-section is shown in Fig 1. More details of device fabrication are given in [7][8][9][10][11].…”