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.
This talk reviews the advantages of low loss silicon nitride photonic integrated circuits. We will present the LIGENTEC offering for low loss SiN PICs for application such as quantum optics, optical computing and telecommunication. Progress on integration of active materials to the low loss platform, such as InP and LNOI are discussed. Integration of actives such as InP reduces the laser linewidth and enables narrow linewidth tunable lasers. The talk reviews the fabrication offering of fast R&D cycles in low volume PIC fabrication though multi-project wafer runs to high volume PIC fabrication in an automotive qualified CMOS line.
In this talk, we present progress on scaling the fabrication of thick film silicon nitride photonics integrated circuits to volume and discuss the advantages of low loss photonic integrated circuits.
We will present the LIGENTEC offering for low loss silicon nitride PICs for application such as quantum, LiDAR and sensing. Options of active integration, such as LNOI are discussed. The offering includes fast R&D cycles in low volume PIC fabrication though multi-project wafer runs to high volume PIC fabrication in an automotive qualified CMOS line.
Mode-locked lasers, and in particular solid-state femtosecond lasers, are oscillators with a unique physics capable to exhibit extremely low-phase noise of the emitted pulse train. Here we report ultra-low phase noise microwave generation with a self-referenced, fully-stabilized mode-locked femtosecond laser. The system involves a 395-MHz repetition rate 1560nm laser which is self-referenced and whose repetition rate is locked to a cavity-stabilized continuous-wave laser. The selfreferencing is achieved with a f-3f nonlinear interferometer realized in a silicon nitride highly-nonlinear waveguide. Prior to optical-to-electrical conversion for X-band microwave generation, the 395-MHz repetition rate of the mode-locked laser pulse train is multiplied in a fiber interleaver to 3.16 GHz. A high-power handling photodiode converts the optical pulse train to an electrical frequency comb with 3.16 GHz frequency spacing. Finally, the 9.5-GHz harmonics is bandpassfiltered and phase noise measurements have shown a record-low phase noise floor of -175 dBc/Hz at 1-MHz offset frequency.
Recent societal demands in climate awareness call for rapid launch of space optical spectrographs, such as to be capable of putting state-of-the-art technology in short timeframe into orbit. As a consequence, it is of paramount importance to compress instruments’ construction schedules down to the ultimately necessary need. Because calibration and characterization (C&C) partially takes place after full instrument assembly, it is de facto on the time-plan critical path, bearing antagonist requirements: measurement accuracy shall be guaranteed without jeopardizing the instrument delivery date. To solve this problem, Airbus has explored multiple paths in order to propose an instrument's "Design for Calibration": the method consists in integrating C&C at the very beginning of the instrument development in order to respond efficiently to the identified needs. First, all planned tests are exhaustively simulated and analyzed with tools validated before measurements, ensuring full control of the overall C&C throughout the entire lifecycle of the project. Next, Airbus strongly enforces its strategy of measuring relevant parameters as soon as they are accessible, hence providing early characterization out of the critical path. Then, the remaining parameters have been thoroughly analyzed to provide a lean optical ground support equipment (OGSE) architecture capable of responding to current challenges. Moreover, it enables full automation, enforcing its time-efficiency by minimizing overheads. Although rapidity is ensured, measurement accuracies are simultaneously kept compliant. Finally, this work presents also disruptive photonics hardware investigated by Airbus to provide calibration for relaxing design: optically filtered supercontinua and optical microcombs.
Photonic Integrated Circuits (PICs) are expected to disrupt the industry similar to what Integrated Circuits did in the electronics industry by shrinking size, weight and cost while increasing performance at the same time. Many optical functions can be integrated in a PIC ranging from a simple beam combiner to a fully integrated optical frequency comb. LIGENTEC's technology addresses today’s challenges of Integrated photonics with low propagation loss, ease of optical coupling and short development cycles. We will present our novel SiN platform for PICs, it’s main functional building blocks and their performance, show effective ways for optical I/Os and a pathway to heterogeneous integration of active elements. Finally, we will discuss application examples in LiDAR, Quantum Computing and RF-optical links in Metrology.
We demonstrate continuous scanning of a dissipative Kerr micro-resonator soliton comb (hereafter called soliton comb). Detuning between a cw pump laser and a resonance of a microresonator is fixed via Pound-Drever-Hall (PDH) locking during scanning so as to maintain soliton operation. We show continuous comb mode scanning of as large as 190 GHz by heating the microresonator. In addition, with the frequency-scanned soliton comb, we demonstrate broadband, high resolution spectroscopy, showing spectral features with a bandwidth of as small as 5 MHz, while covering more than 2 THz spectrum.
In our experiment we use silicon nitride waveguides embedded in silicon dioxide on a silicon chip. The cross section of the waveguide is approximately 1.8µm width by 0.8µm height and the ring resonator has a radius of 120µm. This resonator is coupled to a bus waveguide that is used to couple the continuous wave pump light into the resonator and the light from the resonator out again. The pump laser is an amplified diode laser which provides around 2W of pump power in the bus waveguide on the photonic chip. If the pump light is in resonance with one of the resonances of the resonator we can generate a frequency comb from the pump light via the Kerr nonlinearity of the material. The spacing in between the lines of the frequency comb is close to the free spectral range of the resonator, which is 190 GHz for the resonator used. By tuning the pump laser through the resonance and modulating the power of the pump light we can achieve a stable state with a pulsed-shape waveform circulating inside the microresonator. These states are known as dissipative Kerr soliton states and they are solutions to the Lugiato-Lefever equation, which describes the nonlinear physics of the system. So far they had been experimentally demonstrated in fiber-ring cavities as well as crystalline microresonators. The main benefits of these states for Kerr frequency combs is that they allow for low-noise but broadband frequency combs with low modulation in the spectrum. In our case we report a 3-dB bandwidth of 10THz which is equivalent to sub-30fs pulses inside the resonator. Because of the chosen geometry of the waveguide cross section we also observe an effect which is caused by higher-order dispersion. Higher-order dispersion are terms that describe the dispersion beyond the quadratic group velocity dispersion. In order for dissipative Kerr solitons to form, anomalous group velocity dispersion is required. If higher-order terms are present as well, the soliton can still exist but additional dynamics come into play resulting in so called soliton Cherenkov radiation or a dispersive wave. In our measured spectrum this feature can be easily identified as a local maximum offset from the pump wavelength. In the time domain the soliton Cherenkov radiation manifests itself as an oscillating tail that is attached to the soliton pulse inside the microresonator. Using simulated values for the dispersion and coupled-mode equations to numerically simulate the physics inside the microresonator we can achieve a very good agreement between the experimentally observed and the simulated spectrum. In order to demonstrate that our frequency comb can be used for metrological applications we implement a full stabilization of the frequency comb and achieve a relative stability of 1e-15. Additionally we use the large bandwidth of 2/3 of an octave to implement a 2f-3f-scheme in order to monitor the carrier envelope offset of the frequency comb in a self-referenced manner.
In summary we have observed for the first time a soliton-based, broadband frequency comb in integrated microresonators. These frequency combs are perfectly suited for spectroscopy and data communication applications.
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