III–V gain region/Si waveguide hybrid lasers with InP-based two-storied ridge structure by direct bonding technology

Abstract

We have fabricated III-V gain region/Si waveguide hybrid lasers with an InP-based two-storied ridge structure using a direct bonding technology. Continuous-wave operation at a temperature of 20oC with a threshold current as low as 30 mA was obtained for a hybrid laser consisting of a Fabry-Perot cavity with facets formed on the Si waveguide, and it was achieved thanks to a high optical coupling efficiency of over 80% at the interface between the III-V gain region and the Si waveguide using a two-storied ridge structure and a taper waveguide. The wavelength tunable laser which is comprised of a Si cavity with a loop mirror and double ring filters and III-V gain regions with laser and semiconductor optical amplifier (SOA) sections was demonstrated by utilizing this hybrid structure. It exhibited a wide wavelength tuning range of 48.6 nm and an optical amplification of 10 dB by SOA.

III–V gain region/Si waveguide hybrid lasers by chip-on-wafer hydrophilic bonding process using UV-ozone treatment

“…The details of this structure are described in our previous paper. 37) Figure 9 shows the fabrication procedure for the hybrid laser. Firstly, straight Si waveguide patterns are formed on an SOI wafer with a 220 nm-thick top Si layer by photolithography and reactive ion etching (RIE) process.…”

“…In previous works, we have reported InP-based gain region/Si waveguide hybrid lasers fabricated via the wafer-to-wafer (WtW) direct bonding process with surface activation by fast-atom beam. [35][36][37] An InP-based two-storied ridge structure with two-step taper waveguides has been introduced for the optical coupling of the III-V active and Si waveguide sections, 36,37) and a high optical coupling efficiency at the III-V/Si interface and its very small wavelength dependence have been indicated. By utilizing the features of the two-storied ridge structure, the wide wavelength tuning range operation of InP-based gain region/Si waveguide hybrid tunable lasers and the monolithic integration of a semiconductor optical amplifier to tunable lasers have been demonstrated using the WtW bonding process.…”

“…By utilizing the features of the two-storied ridge structure, the wide wavelength tuning range operation of InP-based gain region/Si waveguide hybrid tunable lasers and the monolithic integration of a semiconductor optical amplifier to tunable lasers have been demonstrated using the WtW bonding process. 36,37) As another point towards the monolithic integration of various functionalities, such as modulators and photodetectors, the chip-on-wafer (CoW) direct bonding process which enables the integration of various types of III-V epitaxial layer structures on a silicon-on-insulator (SOI) wafer is indispensable. [38][39][40] As the bonding process for the InP chips and SOI wafer, we adopted the hydrophilic bonding process using UV-ozone treatment, since surface treatment by UV-ozone is expected to be a low damage and effective hydrophilization process, [41][42][43][44] and we think that this bonding process is very suitable for the fabrication of photonic devices.…”

High thermal performance hybrid GaInAsP/SOI ridge waveguide lasers with enhanced heat dissipation structure

“…The bonding process was previously reported. 25,26) Moreover, the laser structure relied on a 3.5 μm wide III-VIII-V ridge waveguide with a 0.5 μm wide Si waveguide underneath, attached to a highly conductive thermal path to the Si substrate for reduction of thermal resistance. As a result, a single-facet output power of 20 mW and lasing operation up to 110 °C were achieved under CW conditions for a 2.0 mm cavity length.…”

“…However, for hybrid III-V/SOI lasers with external-cavity structures, the SiO 2 layer also acts as vertical cladding for the external Si waveguide with metal microheaters. 26) Figures 1(a) and 1(b) show the calculated optical intensity of the fundamental TE mode using the finite difference method (FDM) at the III-V/ SOI gain section with conventional ridge insulation and an external Si waveguide section, respectively. The SiO 2 cladding layer was characterized by a horizontal cladding height (h y ) and vertical cladding thickness (w x ), as both thicknesses were naturally coupled during plasma-enhanced chemical vapor deposition.…”