High spectral 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 μm wavelength range for microwave and terahertz (THz) generation. Generating a microwave beat frequency near 11 GHz, we observe an 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 (Si3N4) 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 Si3N4 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.

Integrated multi-wavelength lasers for all-optical processing of ultra-high frequency signals

“…2. Multi-wavelength emission can also be obtained from lasers with an intrinsic filtering mechanism selecting different longitudinal modes in their cavity: from Y-shaped or sequential DBR 4,[15][16][17]37 , special patterning of DBR or DFB structures 6,38 , wavelength multiplexing using an arrayed waveguide grating (AWG) 5,11 , see respective illustrations in Fig. 1(c.1)-(c.3) .…”

“…This arguably represents the ideal canvas for the development of MWLs: the opportunity for many groups to test novel ideas and solutions on an open platform that also guarantees mass manufacturability. Thus, many different MWL structures have been proposed taking advantage of the accessibility of these platforms [10][11][12][13][14][15][16][17] . Nevertheless, lasing remains a "winner takes it all" process and, a) Authors to whom correspondence should be addressed: Martin Virte, martin.virte@vub.be; Pablo Marin-Palomo, pablo.marinpalomo@vub.be as such, simultaneous emission at different wavelengths requires a fine adjustment of the gain and is thus quite challenging to achieve.…”

Control of dual-wavelength laser emission via optical feedback phase tuning

“…Embedded gratings were proposed to advance towards reliable sources [23] but this appeared to be insufficient to gain complete control over the dual-wavelength emission of the laser. Different solutions were proposed using quantum-well structures including y-shaped cavities with detuned spectrally selective mirrors [26], [27], [28], [29], [30], such as Distributed Bragg Refletors (DBRs), or engineered reflectors to accomodate emission at two distinct wavelengths [31], [32]. However, these devices somehow faced similar challenges and limitations in terms of control mechanism.…”