Upconversion detector for range-resolved DIAL measurement of atmospheric CH4
L. Meng, A. Fix, M. Wirth, L. Høgstedt, P. Tidemand-Lichtenberg, C. Pedersen, & P. J. Rodrigo
Abstract
We demonstrate a robust, compact, portable and efficient upconversion detector (UCD) for a differential absorption lidar (DIAL) system designed for range-resolved methane (CH4) atmospheric sensing. The UCD is built on an intracavity pump system that mixes a 1064 nm pump laser with the lidar backscatter signal at 1646 nm in a 25-mm long periodically poled lithium niobate crystal. The upconverted signal at 646 nm is detected by a photomultiplier tube (PMT). The UCD with a noise equivalent power around 127 fW/Hz1/2 outperforms a conventional InGaAs based avalanche photodetector when both are used for DIAL measurements. Using the UCD, CH4 DIAL measurements have been performed yielding differential absorption optical depths with relative errors of less than 11% at ranges between 3 km and 9 km.
A picosecond Optical Parametric Oscillator synchronously pumped by an amplified gain-switched laser diode
F. Kienle, K. K. Cheng, S. Alam, C. B. E. Gawith, J. I.Mackenzie, D. C. Hanna, D. J. Richardson, and D. P. Shepherd
Abstract
We demonstrate a picosecond optical parametric oscillator synchronously pumped by a fiber-amplified gain-switched laser diode. Up to 7.3W at 1.54µm and 3.1W at 3.4µm is obtained at pulse repetition rates between 114.8 and 918.4MHz.
Optical Parametric Oscillator within 2.4–4.3 μm Pumped with a Nanosecond Nd:YAG Laser
D. B. Kolker, R. V. Pustovalova, M. K. Starikova, A. I. Karapuzikov, A. A. Karapuzikov, O. M. Kuznetsov, and Yu. V. Kistenev
Abstract
An optical parametric oscillator has been designed on the basis of MgO:PPLN periodic structure. A compact nanosecond Nd:YAG laser has been used as a pump source at 1.053 μm. The pump pulse length is 5–7 ns at a maximum pulse energy of 300 μJ and a frequency of 1000–5000 Hz. The oscillation threshold is 22 μJ at 3 μm and 48 μJ at 4.3 μm. The maximum conversion efficiency from incident pump power to the idler output is 3.9%.
Combining cw-seeding with highly nonlinear fibers in a broadly tunable femtosecond optical parametric amplifier at 42 MHz.
T. Steinle, S. Kedenburg, A. Steinmann, and H. Giessen
Abstract
We report on a precisely tunable and highly stable femtosecond oscillator-pumped optical parametric amplifier at a 41.7 MHz repetition rate for spectroscopic applications. A novel concept based on cw-seeding of a first amplification stage with subsequent spectral broadening and shaping, followed by two further amplification stages, allows for precise sub-nanometer and gap-free tuning from 1.35 to 1.75 μm and 2.55 to 4.5 μm. Excellent spectral stability is demonstrated with deviations of less than 0.008% rms central wavelength and 1.6% rms bandwidth over 1 h. Spectral shaping of the seed pulse allows precise adjustment of both the bandwidth and the pulse duration over a broad range at a given central wavelength. Transform-limited pulses nearly as short as 107 fs are achieved. More than half a Watt of average power in the near- and more than 200 mW in the mid-infrared with power fluctuations less than 0.6% rms over 1 h provide an excellent basis for spectroscopic experiments. The pulse-to-pulse power fluctuations are as small as 1.8%. Further, we demonstrate for the first time, to the best of our knowledge, that by using hollow-core capillaries with highly nonlinear liquids as a host medium for self-phase modulation, the signal tuning range can be extended and covers the region from 1.4 μm up to the point of degeneracy at 2.07 μm. Hence, the idler covers 2.07 to 4.0 μm.
High-energy, near- and mid-IR picosecond pulses generated by a fiber-MOPA-pumped optical parametric generator and amplifier
L. Xu, H.-Y. Chan, S. Alam, D. J. Richardson, and D. P. Shepherd
Abstract
We report a high-energy picosecond optical parametric generator/amplifier (OPG/A) based on a MgO:PPLN crystal pumped by a fiber master-oscillator-power-amplifier (MOPA) employing direct amplification. An OPG tuning range of 1450-3615 nm is demonstrated with pulse energies as high as 2.6 μJ (signal) and 1.2 μJ (idler). When seeded with a ~100 MHz linewidth diode laser, damage-limited pulse energies of 3.1 μJ (signal) and 1.3 μJ (idler) have been achieved and the signal pulse time-bandwidth product is improved to ~2 times transform-limited. When seeded with a 0.3 nm-bandwidth filtered amplified spontaneous emission source, crystal damage is avoided and maximum pulse energies of 3.8 μJ (signal) and 1.7 μJ (idler) are obtained at an overall conversion efficiency of 45%.
Femtosecond OPO based on MgO:PPLN synchronously pumped by a 532nm fiber laser
Jianjun Cao, Dongyi Shen2 Yuanlin Zheng, Yaming Feng, Yan Kong and Wenjie Wan
Abstract
With the rapid progress in fiber technologies, femtosecond fiber lasers, which are compact, cost-effective and stable, have been developed and are commercially available. Studies of optical parametric oscillators (OPOs) pumped by this type of laser are demanding. Here we report a femtosecond optical parametric oscillator (OPO) at 79.6 MHz repetition rate based on MgO-doped periodically poled LiNbO3 (MgO:PPLN), synchronously pumped by the integrated second harmonic radiation of a femtosecond fiber laser at 532 nm. The signal delivered by the single resonant OPO is continuously tunable from 757 to 797 nm by tuning the crystal temperature in a poling period of 7.7 µm. The output signal shows good beam quality in TEM00 mode profile with pulse duration of 206 fs at 771 nm. Maximum output signal power of 71 mW is obtained for a pump power of 763 mW and a low pumping threshold of 210 mW is measured. Moreover, grating tuning and cavity length tuning of the signal wavelength are also investigated.
Broadband and tunable optical parametric generator for remote detection of gas molecules in the short and mid-infrared
S. Lambert-Girard, M. Allard, M. Piché, and F. Babin
Abstract
The development of a novel broadband and tunable optical parametric generator (OPG) is presented. The OPG properties are studied numerically and experimentally in order to optimize the generator’s use in a broadband spectroscopic LIDAR operating in the short and mid-infrared. This paper discusses trade-offs to be made on the properties of the pump, crystal, and seeding signal in order to optimize the pulse spectral density and divergence while enabling energy scaling. A seed with a large spectral bandwidth is shown to enhance the pulse-to-pulse stability and optimize the pulse spectral density. A numerical model shows excellent agreement with output power measurements; the model predicts that a pump having a large number of longitudinal modes improves conversion efficiency and pulse stability.
DFG-based mid-IR generation using a compact dual-wavelength all-fiber amplifier for laser spectroscopy applications
K. Krzempek, G. Sobon, and K. M. Abramski
Abstract
We demonstrate a compact mid-infrared (mid-IR) radiation source based on difference frequency generation (DFG) in periodically poled lithium niobate (PPLN) crystal. The system incorporates a dual-wavelength master oscillator power amplifier (MOPA) source capable of simultaneous amplification of 1064 nm and 1548 nm signals in a common active fiber co-doped with erbium and ytterbium ions. Two low-power seed lasers were amplified by a factor of 14.4 dB and 23.7 dB for 1064 nm and 1548 nm, respectively and used in a nonlinear DFG setup to generate 1.14 mW of radiation centered at 3.4 μm. The system allowed for open-path detection of methane (CH4) in ambient air with estimated minimum detectable concentration at a level of 26 ppbv.
Fully-integrated dual-wavelength all-fiber source for mode-locked square-shaped mid-IR pulse generation via DFG in PPLN
Karol Krzempek, Grzegorz Sobon, Jaroslaw Sotor, and Krzysztof M. Abramski
Abstract
First demonstration of a dissipative soliton resonance (DSR), double-clad (DC) active fiber, mode-locked figure-8 laser (F8L) enabling simultaneous amplification of 1064 nm seed signal is presented. Appropriate design supported peak power clamping (PPC) effect in the laser resonator and enabled easy tuning of the generated, square-shaped pulses from 20 ns to 170 ns. By incorporating a circulator-based isolating element in the directional loop of the laser, record pulse energy of 2.13 μJ was achieved, directly at the output of the resonator. The usability of the unique dual-wavelength design was experimentally put to a test in a difference frequency generation (DFG) setup using periodically poled lithium niobate (PPLN) crystal.
In this Letter, we demonstrate efficient room temperature detection of ultra-broadband mid-wave-infrared (MWIR) light with an almost flat response over more than 1200 nm, exploiting an efficient nonlinear upconversion technique. Black-body radiation from a hot soldering iron rod is used as the IR test source. Placing a 20 mm long periodically poled lithium niobate crystal in a compact intra-cavity setup (>20 W CW pump at 1064 nm), MWIR wavelengths ranging from 3.6 to 4.85 μm are upconverted to near-infrared (NIR) wavelengths (820–870 nm). The NIR light is detected using a standard low-noise silicon-based camera/grating spectrometer. The proposed technique allows high conversion efficiency over a wider bandwidth without any need for a shorter crystal length. Different analytical predictions and numerical simulations are performed a priori to support the experimental demonstrations.
