Vincent Michaud-Belleau

Whispering gallery mode sensing with a dual frequency comb probe

Silica microspheres are probed with a dual comb interferometry setup. The impulse responses of these microresonators are measured with a temporal resolution smaller than 400 fs over more than 200 ps. The amplitudes and phases of the impulse responses are interpreted as providing sensing information. The more familiar transmission spectra corresponding to the measured impulse responses are also calculated and shown. Sensing is demonstrated by varying the concentration of isopropanol in de-ionized water surrounding the microsphere and by binding bovine serum albumin on the silanized microsphere surface.

All-fiber DFB laser operating at 2.8 μm

Single-frequency laser emission from a distributed feedback all-fiber laser operating in the vicinity of 3xa0μm is demonstrated. The laser cavity was made of a 30xa0mm long π-phase-shifted fiber Bragg grating inscribed in a heavily erbium-doped fluoride fiber using infrared femtosecond pulses and the dithering phase-mask technique. A maximum CW output power of 12xa0mW was obtained at 2794.4xa0nm by using a multimode pumping scheme. The narrow linewidth was characterized to be lower than 20xa0kHz using a heterodyne technique. This achievement represents a significant step toward the development of active frequency references operating in the mid-infrared.

Self-heterodyne interference spectroscopy using a comb generated by pseudo-random modulation.

We present an original instrument designed to accomplish high-speed spectroscopy of individual optical lines based on a frequency comb generated by pseudo-random phase modulation of a continuous-wave (CW) laser. This approach delivers efficient usage of the laser power as well as independent control over the spectral point spacing, bandwidth and central wavelength of the comb. The comb is mixed with a local oscillator generated from the same CW laser frequency-shifted by an acousto-optic modulator, enabling a self-heterodyne detection scheme. The current configuration offers a calibrated spectrum every 1.12 µs. We demonstrate the capabilities of the spectrometer by producing averaged, as well as time-resolved, spectra of the D1 transition of cesium with a 9.8-MHz point spacing, a 50-kHz resolution and a span of more than 3 GHz. The spectra obtained after 1 ms of averaging are fitted with complex Voigt profiles that return parameters in good agreement with expected values.

Holmium-doped 2.1 μm waveguide chip laser with an output power > 1 W

We demonstrate the increasing applicability of compact ultra-fast laser inscribed glass guided-wave lasers and report the highest-power glass waveguide laser with over 1.1 W of output power in monolithic operation in the short-infrared near 2070 nm achieved (51% incident slope efficiency). The holmium doped ZBLAN chip laser is in-band pumped by a 1945 nm thulium fiber laser. When operated in an extended-cavity configuration, over 1 W of output power is realized in a linearly polarized beam. Broad and continuous tunability of the extended-cavity laser is demonstrated from 2004 nm to 2099 nm. Considering its excellent beam quality of M² = 1.08, this laser shows potential as a flexible master oscillator for single frequency and mode-locking applications.

Dual-comb spectroscopy with a phase-modulated probe comb for sub-MHz spectral sampling.

We present a straightforward and efficient method to reduce the mode spacing of a frequency comb based on binary pseudo-random phase modulation of its pulse train. As a proof of concept, we use such a densified comb to perform dual-comb spectroscopy of a long-delay Mach-Zehnder interferometer and a high-quality-factor microresonator with sub-MHz spectral sampling. Since this approach is based on binary phase modulation, it combines all the advantages of other densification techniques: simplicity, single-step implementation, and conservation of the initial combs power.

Passive coherent discriminator using phase diversity for the simultaneous measurement of frequency noise and intensity noise of a continuous-wave laser

The frequency noise and intensity noise of a laser set the performance limits in many modern photonics applications and, consequently, must often be characterized. As lasers continue to improve, the measurement of these noises however becomes increasingly challenging. Current approaches for the characterization of very high-performance lasers often call for a second laser with equal or higher performance to the one that is to be measured, an incoherent interferometer having an extremely long delay-arm, or an interferometer that relies on an active device. These instrumental features can be impractical or problematic under certain experimental conditions. As an alternative, this paper presents an entirely passive coherent interferometer that employs an optical 90° hybrid coupler to perform in-phase and quadrature detection. We demonstrate the technique by measuring the frequency noise power spectral density of a highly-stable 192 THz (1560 nm) fiber laser over five frequency decades. Simultaneously, we are able to measure its relative intensity noise power spectral density and characterize the correlation between its amplitude noise and phase noise. We correct some common misconceptions through a detailed theoretical analysis and demonstrate the necessity to account for normal imperfections of the optical 90° hybrid coupler. We finally conclude that this passive coherent discriminator is suitable for reliable and simple noise characterization of highly-stable lasers, with bandwidth and dynamic range benefits but susceptibility to additive noise contamination.

An open and flexible digital phase-locked loop for optical metrology

This paper presents an open and flexible digital phase-locked loop optimized for laser stabilization systems. It is implemented on a cheap and easily accessible FPGA-based digital electronics platform (Red Pitaya) running a customizable open-source firmware. A PC-based software interface allows controlling the platform and optimizing the loop parameters remotely. Several tools are included to allow measurement of quantities of interest smoothly and rapidly. To demonstrate the platforms capabilities, we built a fiber noise canceller over a 400 m fiber link. Noise cancellation was achieved over a 30 kHz bandwidth, a value limited mainly by the delays introduced by the actuator and by the round-trip propagation over the fiber link. We measured a total latency of 565 ns for the platform itself, limiting the theoretically achievable control bandwidth to approximately 225 kHz.

Passive coherent discriminator using phase diversity for the measurement of CW laser frequency noise

We present a short-delay fiber interferometer that employs a 90° optical hybrid to perform in-phase and quadrature detection. This instrument allows a passive and robust characterization of the frequency noise of highly stable laser oscillators.

Dense Spectral Sampling Dual-Comb Spectroscopy through Pseudo-Random Phase Modulation of the Probe Comb

We introduce an efficient and simple technique to reduce the mode spacing of a frequency comb. We use such a densified comb in multiheterodyne configuration to characterize a microresonator displaying resonances that are otherwise unresolved.

Tunable single-frequency DFB fiber laser at 2.8 μm

We report a tunable single-frequency laser emission near 2.8 μm from an all-fiber distributed feedback laser. A 20 kHz linewidth is measured with a tunability of ~1 nm at a step resolution of 3 pm.