Versatile short-wave and mid-infrared sources based on wideband parametric conversion

The mid-infrared part of the optical spectrum is of high interest in a wide range of applications such as environmental gas monitoring, contaminant detection in the chemical, food or pharmaceutical industry, medical diagnosis, or defense and security. Relevant molecules can readily be identified through their mid-infrared absorption spectra, as the latter contains the fundamental resonances of a number of pollutant and toxic gases. Consequently, spectroscopic apparatus, light detection and ranging systems or free-space communication links all benefit from the progress accomplished by mid-infrared technologies over the last years. However some shortcomings in the light emitters capabilities are still to be addressed. In this research work, we aim at designing a mid-infrared laser as versatile as possible and based on nonlinear wavelength conversion. The conversion relies on third-order parametric effects in waveguides such as optical fibers made of various types of glass, or integrated semiconductor chips. The objective is to leverage mature communication-band components to generate and shape the seed optical signals, then mixed in the abovementioned waveguides to down-convert them towards midinfrared. The wavelength conversion is performed in two stages, and the first stage consists of a parametric source emitting in the short-wave infrared range. This thesis mostly focuses on the design and realization of this stage. As such, it is closely linked to the field of nonlinear fiber optics, where the use of silica is preponderant. We build on the research performed over the last years on parametric amplifiers, initially used for the re-amplification of communication signals, and we combine it with technologies dedicated to short-wave infrared fiber lasers. As such, we are able to build wavelength tunable and modulation-capable short-wave infrared sources, significantly more powerful and versatile than previous broadband parametric converter designs. The end of the dissertation is then dedicated to the solutions that are then envisioned to realize the second conversion stage, towards mid-infrared. Very promising numerical and experimental results indicate a successful outcome to the project, confirming the validity of the laser concept

Large second harmonic generation enhancement in SiN waveguides by all-optically induced quasi phase matching

Integrated waveguides exhibiting efficient second-order nonlinearities are crucial to obtain compact and low power optical signal processing devices. Silicon nitride (SiN) has shown second harmonic generation (SHG) capabilities in resonant structures and single-pass devices leveraging intermodal phase matching, which is defined by waveguide design. Lithium niobate allows compensating for the phase mismatch using periodically poled waveguides, however the latter are not reconfigurable and remain difficult to integrate with SiN or silicon (Si) circuits. Here we show the all-optical enhancement of SHG in SiN waveguides by more than 30 dB. We demonstrate that a Watt-level laser causes a periodic modification of the waveguide second-order susceptibility. The resulting second order nonlinear grating has a periodicity allowing for quasi phase matching (QPM) between the pump and SH mode. Moreover, changing the pump wavelength or polarization updates the period, relaxing phase matching constraints imposed by the waveguide geometry. We show that the grating is long term inscribed in the waveguides, and we estimate a second order nonlinearity of the order of 0.3 pm/V, while a maximum conversion efficiency (CE) of 1.8x10-6 W-1 cm-2 is reached

Efficient broadband parametric conversion: reaching for the Mid IR

In this paper, we report recent results on the efficient generation of SWIR sources exploiting broadband wavelength conversion in silica fibers. Optimized cavity-less designs of fiber parametric amplifiers (FOPA) associated with Thulium amplification capable of high CW powers, wide tunability and modulation will be presented. We also present how parametric conversion can be extended deeper in the Mid-IR by engineering of non-silica mixing platforms

Kerr nonlinearity and dispersion characterization of core-pumped thulium-doped fiber at 2 μm

A nonlinear coefficient of 3.6–4.1 W−1 km−1 and group velocity dispersion of −20 ps2∕km of a commercial corepumped thulium-doped fiber have been evaluated using degenerate four-wave mixing at 2 μm. The anomalous dispersion behavior of the fiber has been confirmed by linear measurements with an all-fiber Mach–Zehnder interferometer (MZI). Additionally, no pump-induced dispersion changes due to excitation of Tm3 cations have been detected. These characteristics make these fibers attractive for pulsed fiber laser applications. A nonlinear polarization rotation mode-locked laser involving nonlinear polarization evolution directly in the doped fiber is demonstrated

Broadly tunable source around 2050 nm based on wideband parametric conversion and thulium–holmium amplification cascade

We report the design of a short-wave infrared continuous-wave light source featuring a 20 mW average output power, and with a wavelength that can be freely selected in the 2000-2100 nm range amid a low power ripple. The operating principle relies on the simultaneous broadband parametric conversion of two seeds in a highly nonlinear silica fiber pumped in the L-band followed by amplification and equalization in an appended thulium- and holmium- doped fiber cascade directly pumped by their respective previous stage

Versatile High Repetition Rate 2-μm Pulsed Source Based on Wideband Parametric Conversion

We report an all-fiber pulsed source based on parametric conversion followed by thulium amplification able to deliver picosecond pulses at a repetition rate selectable between 2 and 5 GHz, of which central wavelength can be freely selected in the 2-μm region. A very versatile Nyquist pulse shaping of the parametric pump, which allows for the electrical control of the pulse train, enables such a freedom in the repetition rate selection, as well as some control in the pulse duration. We also show that data can be embedded in the output pulse train resulting in a high-quality Gb/s return-to-zero transmitter. Such a programmable short-wave infrared laser is of high interest for sensing or nonlinear optics applications around 2000 nm that require a fine adjustment in both the spectral and temporal domains

Versatile high repetition rate 2 micron pulsed source based on wideband parametric conversion

We report an all-fiber pulsed source based on parametric conversion followed by thulium amplification able to deliver picosecond pulses at a repetition rate selectable between 2 and 5 GHz, of which central wavelength can be freely selected in the 2 micron region. A very versatile Nyquist pulse shaping of the parametric pump, which allows for the electrical control of the pulse train, enables such a freedom in the repetition rate selection, as well as some control in the pulse duration. We also show that data can be embedded in the output pulse train resulting in a high quality Gb/s return-to-zero transmitter. Such a programmable short-wave infrared laser is of high interest for sensing or nonlinear optics applications around 2000 nm that require a fine adjustment in both the spectral and temporal domains

Tunable Thulium-Assisted Parametric Generation of 10 Gb/s Intensity Modulated Signals Near 2 μm

We report the demonstration of an all-fiber 10Gb/s modulation capable source near 2μm, tunable over more than 60nm with powers exceeding 2dBm, based on parametric conversion and appended Thulium amplification

Thulium Assisted Parametric Conversion from Near to Short Wave Infrared

We report an all-fiber continuous wave source, tunable between 1935-1980nm, based on parametric conversion combined with thulium amplification. More than 150mW of power and 30dB optical signal-to-noise ratio is obtained over the entire range. OCIS codes: (190.4975) Parametric processes, (230.2285) Fiber devices and optical amplifiers, (060.4370) Nonlinear optics, fibers

Widely Tunable Picosecond-Pulsed Source near 2 μm based on Cascaded Raman Wavelength Shifting

We demonstrate a cavity-less picosecond pulsed source near 2μm, tunable over more than 200nm based on third order cascaded Raman wavelength shifting. Up to 44% conversion is achieved for 100mW peak powers at 200MHz repetition rate