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.V Michaud-Belleau, H Bergeron, P S Light, N B Hébert, J D Deschênes, A N Luiten and J Genes

Single-frequency mid-infrared waveguide laser

A guided-wave chip laser operating in a single longitudinal mode at 2860 nm is presented. The cavity was set in the Littman-Metcalf configuration to achieve single-frequency operation with a side-mode suppression ratio above 33 dB. The chip laser’s 2 MHz linewidth on a 10 ms scale was found to be limited by mechanical fluctuations, but its Lorentzian contribution was estimated to be lower than 1 Hz using a heterodyne technique. This demonstration incorporates a high coherence source with the simplicity provided by the compactness of chip lasers.Philippe Guay, Jérôme Genest, Vincent Michaud-Belleau, Nicolas Bourbeau Hébert, and David G. Lancaste

Real-time dynamic atomic spectroscopy using electro-optic frequency combs

Published 25 October 2016Spectroscopy is a key technology for both fundamental and applied science. A long-held desire has been the development of a means to continuously acquire broadband spectral data with simultaneous high time and frequency resolution. Frequency-comb technology can open this door: here, we use a spectroscopic technique based on an electro-optic comb to make continuous observations of cesium vapor across a 3.2-GHz spectral bandwidth with a 2-μs time resolution and with 10-MHz frequency sampling. We use a rapidly switched pump laser to burn narrow features into the spectral line and study the response to this step perturbation. This examination allows us to see a number of unexpected effects, including the temporal evolution of the bandwidth, the amplitude, and the frequency of these burnt features. We also report on the previously unobserved effect of radiation reabsorption, which slowly produces a broad pedestal of perturbation around each feature. We present models that can explain these dynamical effects.Nicolas Bourbeau Hébert, Vincent Michaud-Belleau, Christopher Perrella, Gar-Wing Truong, James D. Anstie, Thomas M. Stace, Jérôme Genest, and Andre N. Luite

Free-running optical frequency combs for remote sensing

From the session: New Techniques for Laser Sensing (ETu3A)Software correction algorithms allow using free-running frequency combs in remote sensing applications. One recent example is the spectroscopy of methane's R and Q branches (2n3 band) with a broadband, rugged, and compact chip-based dual-comb system.Philippe Guay, Nicolas Bourbeau Hébert, Vincent Michaud-Belleau, David G. Lancaster, Jerome Genes

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.Nicolas Bourbeau Hébert, Vincent Michaud-Belleau, James D. Anstie, Jean-Daniel Deschênes, Andre N. Luiten, and Jérôme Genes

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.7 page(s

Dual electro-optic frequency comb spectroscopy using pseudo-random modulation

Abstract not available.Khaoula Fdil, Vincent Michaud-Belleau, Nicolas Bourbeau Hébert, Philippe Guay, Adam J. Fleisher, Jean-Daniel Deschênes, and Jéróme Genes