Wideband tunable laser phase noise reduction using single sideband modulation in an electro-optical feed-forward scheme

Modulation-free laser stabilization technique using integrated cavity-coupled Mach-Zehnder interferometer

Stable lasers play a significant role in precision optical systems where an electro-optic laser frequency stabilization system, such as the Pound-Drever-Hall technique, measures laser frequency and actively stabilizes it by comparing it to a frequency reference. Despite their excellent performance, there has been a trade-off between complexity, scalability, and noise measurement sensitivity. Here, we propose and experimentally demonstrate a modulation-free laser stabilization method using an integrated cavity-coupled Mach-Zehnder interferometer as a frequency noise discriminator. The proposed architecture maintains the sensitivity of the Pound-Drever-Hall architecture without the need for any modulation. This significantly simplifies the architecture and makes miniaturization into an integrated photonic platform easier. The implemented chip suppresses the frequency noise of a semiconductor laser by 4 orders-of-magnitude using an on-chip silicon microresonator with a quality factor of 2.5 × 106. The implemented passive photonic chip occupies an area of 0.456 mm2 and is integrated on AIM Photonics 100 nm silicon-on-insulator process.

Broadly tunable and ultra-highly selective detection of radio frequency signals enabled by a silicon photonic chip

Precise and agile detection of radio frequency (RF) signals over an ultra-wide frequency range is a key functionality in modern communication, radar, and surveillance systems, as well as for radio astronomy and laboratory testing. However, current microwave solutions are inadequate for achieving the needed high performance in a chip-scale format, with the desired reduced cost, size, weight, and power. Photonics-based technologies have been identified as a potential solution but the need to compensate for the inherent noise of the involved laser sources have prevented on-chip realization of wideband RF signal detection systems. Here, we report an approach for ultra-wide range, highly-accurate detection of RF signals using a conceptually novel feed-forward laser's noise cancelling architecture integrated on chip. The technique is applied to realization of an RF scanning receiver as well as a complete radar transceiver integrated on a CMOS-compatible silicon-photonics chip, offering an unprecedented selectivity > 80 dB, spectral resolution < 1 kHz, and tunability in the full 0.5-35 GHz range. The reported work represents a significant step towards the development of integrated system-on-chip platforms for signal detection, analysis and processing in cognitive communication and radar network applications.

Integrated coherent optical receiver with feed-forward carrier recovery

Coherent optical communication provides optical links with a high spectral efficiency and sensitivity. An essential feature of a coherent optical receiver is to phase lock the optical local oscillator to the carrier of the incoming signal. In this work, we propose and demonstrate, for the first time, a novel coherent optical receiver, where the relative instantaneous phase between the incoming optical carrier and a semiconductor laser (SCL), serving as the optical local oscillator, is first detected using a balanced photodiode, filtered, and used in a feed-forward scheme to modify the phase of the optical local oscillator, effectively recovering the input carrier, which is then used for data recovery. The proposed architecture leverages high-performance on-chip photonic devices to realize a low-power coherent optical receiver without utilizing a phase-locked loop and eliminates the required high data-rate ADC, lowering the complexity of the backend DSP. The photonic part of the implemented prototype was integrated on a 180 nm silicon-on-insulator photonic process within a footprint of 1.0 mm × 0.8 mm. Clock and data recovery at 10 GBaud/s with bit-error-rates better than 10^-6 and 10^-3 for optical BPSK and QPSK have been demonstrated, respectively.

Numerical investigation of a feed-forward linewidth reduction scheme using a mode-locked laser model of reduced complexity

We provide numerical verification of a feed-forward, heterodyne-based phase noise reduction scheme using single-sideband modulation that obviates the need for optical filtering at the output. The main benefit of a feed-forward heterodyne linewidth reduction scheme is the simultaneous reduction of the linewidth of all modes of a mode-locked laser (MLL) to that of a narrow-linewidth single-wavelength laser. At the heart of our simulator is an MLL model of reduced complexity. Importantly, the main issue being treated is the jitter of MLLs and we show how to create numerical waveforms that mimic the random-walk nature of timing jitter of pulses from MLLs. Thus, the model does not need to solve stochastic differential equations that describe the MLL dynamics, and the model calculates self-consistently the line-broadening of the modes of the MLL and shows good agreement with both the optical linewidth and jitter. The linewidth broadening of the MLL modes are calculated after the phase noise reduction scheme and we confirm that the phase noise contribution from the timing jitter still remains. Finally, we use the MLL model and phase noise reduction simulator within an optical communications system simulator and show that the phase noise reduction technique could enable MLLs as optical carriers for higher-order modulation formats, such as 16-state and 64-state quadrature amplitude modulation.

Integrated Pound-Drever-Hall laser stabilization system in silicon

Low noise stable lasers have far-reaching applications in spectroscopy, communication, metrology and basic science. The Pound−Drever−Hall laser stabilization technique is widely used to stabilize different types of lasers in these areas. Here we report the demonstration of an integrated Pound−Drever−Hall system that can stabilize a low-cost laser to realize a compact inexpensive light source, which can ultimately impact many fields of science and engineering. We present an integrated architecture utilizing an electronically reconfigurable Mach−Zehnder interferometer as the frequency reference to reduce the frequency noise of semiconductor lasers by more than 25 dB and the relative Allan deviation by more than 12 times at 200 μs averaging time. Compared to the bench-top implementations, the integrated Pound−Drever−Hall system has significantly lower power consumption, less sensitivity to the environmental fluctuations and occupies an area of only 2.38 mm². The photonic and electronic devices are integrated on a standard 180 nm complementary metal-oxide semiconductor silicon-on-insulator process.

Frequency-stable laser systems are important for many applications, like optical communications, that require high precision and low noise. Here, Idjadi and Aflatouni demonstrate that the widely used Pound-Drever-Hall technique can be fully integrated on-chip, miniaturizing the stabilization setup.

Note: Efficient diode laser line narrowing using dual, feed-forward + feed-back laser frequency control

We have achieved distributed feedback laser diode line narrowing by simultaneously acting on the diode current via a feed-back loop and on an external electrooptic phase modulator in feed-forward actuator. This configuration turns out to be very efficient in reaching large bandwidth in the phase correction: up to 15 MHz with commercial laser control units. About 98% of the laser power undergoes narrowing. The full width at half maximum of the narrowed optical spectrum is of less than 4 kHz. This configuration appears to be very convenient as the delay in the feed-forward control electronics is easily compensated for by a 20 m optical fiber roll.

Performance and noise analysis of optical microresonator-based biochemical sensors using intensity detection

Optical microcavity sensors using intensity detection open up the possibility to realize fully integrated high-performance sensing devices, which are significant for both fundamental study of molecular interaction and rapid disease diagnosis. Although the performance of microresonator-based sensors has been studied focusing on the resonance-tracking method, the situation can be much different for intensity-detection sensors. Here we conducted a systematically investigation on the noises sources in intensity detection scheme and their influences on key performance parameters, e.g., signal-to-noise ratio (SNR), limit-of-detection (LOD), and detection range, for various sensors configurations. Especially, the trade-off between SNR and LOD is identified and theoretically analyzed. With experiment noises taken into consideration, our work aims to provide design guidelines for integrated microresonator sensors with optimized performance.

An efficient technique for the reduction of wavelength noise in resonance-based integrated photonic sensors

A systematic study of the limit of detection (LOD) in resonance-based silicon photonic lab-on-chip sensors is presented.