The hybrid vertical-cavity laser is a potential low current, high-efficiency, and small footprint light source for silicon photonics integration. As part of the development of such light sources we demonstrate hybrid-cavity VCSELs (HC-VCSELs) on silicon where a GaAs-based half-VCSEL is attached to a dielectric distributed Bragg reflector on silicon by adhesive bonding. HC-VCSELs at 850 nm with sub-mA threshold current, >2 mW output power, and 25 Gbit/s modulation speed are demonstrated. Integration of short-wavelength lasers will enable fully integrated photonic circuits on a silicon-nitride waveguide platform on silicon for applications in life science, bio-photonics, and short-reach optical interconnects.
We present a vertical-cavity surface-emitting laser (VCSEL) where a GaAs-based “half-VCSEL” is attached to a
dielectric distributed Bragg reflector on silicon using ultra-thin divinylsiloxane-bis-benzocyclobutene (DVS-BCB)
adhesive bonding, creating a hybrid cavity where the optical field extends over both the GaAs- and the Si-based parts of
the cavity. A VCSEL with an oxide aperture diameter of 5 μm and a threshold current of 0.4 mA provides 0.6 mW
output power at 845 nm. The VCSEL exhibits a modulation bandwidth of 11 GHz and can transmit data up to 20 Gbps.
We present a GaAs-based VCSEL structure, BCB bonded to a Si<sub>3</sub>N<sub>4</sub> waveguide circuit, where one DBR is substituted by
a free-standing Si<sub>3</sub>N<sub>4</sub> high-contrast-grating (HCG) reflector realized in the Si<sub>3</sub>N<sub>4</sub> waveguide layer. This design enables
solutions for on-chip spectroscopic sensing, and the dense integration of 850-nm WDM data communication transmitters
where individual channel wavelengths are set by varying the HCG parameters. RCWA shows that a 300nm-thick Si<sub>3</sub>N<sub>4</sub>
HCG with 800nm period and 40% duty cycle reflects strongly (<99%) over a 75nm wavelength range around 850nm. A
design with a standing-optical-field minimum at the III-V/airgap interface maximizes the HCG’s influence on the
VCSEL wavelength, allowing for a 15-nm-wide wavelength setting range with low threshold gain (<1000 cm<sup>-1</sup>).