High-purity microwave generation using a dual-frequency hybrid integrated semiconductor-dielectric waveguide laser

Abstract

We present an integrated semiconductor-dielectric hybrid dual-frequency laser operating in the 1.5 $\mu$m wavelength range for microwave and terahertz (THz) generation. Generating a microwave beat frequency near 11 GHz, we observe a record-narrow intrinsic linewidth as low as about 2 kHz. This is realized by hybrid integration of a single diode amplifier based on indium phosphide (InP) with a long, low-loss silicon nitride (Si${}_3$N${}_4$) feedback circuit to extend the cavity photon lifetime, resulting in a cavity optical roundtrip length of about 30 cm on a chip. Simultaneous lasing at two frequencies is enabled by introducing an external control parameter for balancing the feedback from two tunable, frequency-selective Vernier mirrors on the Si${}_3$N${}_4$ chip. Each frequency can be tuned with a wavelength coverage of about 80 nm, potentially allowing for the generation of a broad range of frequencies in the microwave range up to the THz range.

References in corpus (7)

• Ultra-low noise microwave generation with fiber-based optical frequency comb and application to atomic fountain clock
• Ultra-narrow linewidth hybrid integrated semiconductor laser
• 25 kHz narrow spectral bandwidth of a wavelength tunable diode laser with a short waveguide-based external cavity
• Ring resonator enhanced mode-hop-free wavelength tuning of an integrated extended-cavity laser
• Unveiling spectral purity and tunability of terahertz quantum cascade laser sources based on intra-cavity difference frequency generation
• Integrated frequency comb laser with narrow intrinsic optical linewidth based on a dielectric waveguide feedback circuit
• InP femtosecond mode-locked laser in a compound feedback cavity with a switchable repetition rate