Continuous-wave (CW) laser-driven integrated Kerr microresonators enable broadband optical frequency combs with high repetition rates and low threshold power, in a compact footprint. A drawback of such microcombs is the low conversion efficiency from the pump laser to the comb lines, which is often in the few percent range or below. Here, complementing previously demonstrated approaches to increase conversion efficiency, we demonstrate a novel approach that leverages a chip-based rare-earth (Tm3+)-doped optical gain medium to boost the pump-to-comb conversion efficiency by more than one order of magnitude. Importantly, the gain medium does not require an additional pump laser, but recycles residual pump light from the Kerr-comb: the CW pump of the Kerr-comb (1610 nm) coincides with the pump wavelength of the on-chip gain medium, allowing unconverted pump power to be absorbed and transferred to the comb lines within gain window (1700 - 1900 nm). This enables a new class of highly efficient Kerr-combs for applications e.g. in data centers and optical computing.
Amplification of ultrafast optical pulses is key to a large number of applications in photonics. While ultrashort pulse amplification is well established in optical gain fibers, it is challenging to achieve in photonic-chip integrated waveguides, due to their inherent high-optical nonlinearity.
Here, we demonstrate for the first-time femtosecond pulse amplification on an integrated photonic chip. Our approach translates the concept of chirped pulse amplification to the chip level. Specifically, we leverage tailored all-normal dispersion, large mode-area gain waveguides to realize a low-nonlinearity, high-gain, short-length optical amplifier in which pulse propagation is dominated by dispersion. We show more than 17dB amplification of ultrashort pulses from a 1 GHz femtosecond source at center wavelength of 1815 nm. The amplified pulses have an on-chip output pulse peak power of 800 W with a pulse duration of 116 fs.
We present on recent progress on a hybrid tellurite glass and silicon nitride photonic platform. We show low loss waveguides and Q factors < 10^6 in microring resonators. We also show rare-earth-doped active devices, including erbium-doped and thulium-doped waveguide amplifiers and thulium-doped microring lasers. Using the same approach, we demonstrate nonlinear functionalities including efficient four-wave-mixing, supercontinuum generation and third harmonic generation in compact microring resonators and waveguides. The platform is highly promising for compact and low-cost passive, active and nonlinear photonic integrated circuits for applications in computing, communications, sensing and metrology.
Mode-locked lasers provide extremely low jitter optical pulse trains for a number of applications ranging from sampling of RF-signals and optical frequency combs to microwave and optical signal synthesis. Integrated versions have the advantage of high reliability, low cost and compact. Here, we describe a fully integrated mode-locked laser architecture on a CMOS platform that utilizes rare-earth doped gain media, double-chirped waveguide gratings for dispersion compensation and nonlinear Michelson Interferometers for generating an artificial saturable absorber to implement additive pulse mode locking on chip. First results of devices at 1.9 μm using thulium doped aluminum-oxide glass and operating in the Q-switched mode locking regime are presented.
We report ultra-narrow-linewidth erbium-doped aluminum oxide (Al2O3:Er3+) distributed feedback (DFB) lasers with a wavelength-insensitive silicon-compatible waveguide design. The waveguide consists of five silicon nitride (SiNx) segments buried under silicon dioxide (SiO2) with a layer Al2O3:Er3+ deposited on top. This design has a high confinement factor (> 85%) and a near perfect (> 98%) intensity overlap for an octave-spanning range across near infrared wavelengths (950–2000 nm). We compare the performance of DFB lasers in discrete quarter phase shifted (QPS) cavity and distributed phase shifted (DPS) cavity. Using QPS-DFB configuration, we obtain maximum output powers of 0.41 mW, 0.76 mW, and 0.47 mW at widely spaced wavelengths within both the C and L bands of the erbium gain spectrum (1536 nm, 1566 nm, and 1596 nm). In a DPS cavity, we achieve an order of magnitude improvement in maximum output power (5.43 mW) and a side mode suppression ratio (SMSR) of > 59.4 dB at an emission wavelength of 1565 nm. We observe an ultra-narrow linewidth of ΔνDPS = 5.3 ± 0.3 kHz for the DPS-DFB laser, as compared to ΔγQPS = 30.4 ± 1.1 kHz for the QPS-DFB laser, measured by a recirculating self-heterodyne delayed interferometer (RSHDI). Even narrower linewidth can be achieved by mechanical stabilization of the setup, increasing the pump absorption efficiency, increasing the output power, or enhancing the cavity Q.
In this work silicon pillar waveguides have been proposed to exploit the entire transparent window of silicon. These geometries posses a broad and at dispersion (from 2 to 6 μm) with four zero dispersion wavelengths. We calculate supercontinuum generation spanning over two octaves (2 to >8 μm) with long wavelengths interacting weakly with the lossy substrate. These structures have higher mode confinement in the silicon - away from the substrate, which makes them substrate independent and are promising for exploring new nonlinear phenomena and highly sensitive molecular sensing over the entire silicon's transparency range
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