Abstract
We report on high power, single-frequency operation of a compact Tm:Y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ceramic laser in 2 μm spectral region employing a volume Bragg grating in a simple linear resonator to serve simultaneously as a resonator mirror and mode selector. The home developed laser quality Tm:Y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ceramic sample has a Tm doped concentration of 2 at.% and pumped with a fiber coupled 793 nm laser diode. Up to 1.5 W of CW single frequency output power at 2014.9 nm has been generated, corresponding to a slope efficiency of 37.9% with respect to absorbed pump power. M <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> factor of the output beam was measured to be ∼1.03.
Highlights
High power, high spectral purity and compact laser sources operating in 2 μm spectral region are of interest for a variety of applications, including medicine, LIDAR, spectroscopy, gas sensing, materials processing and various defence-related applications [1]–[4]
Volume Bragg gratings (VBG) inscribed in photo-thermal refractive (PTR) glasses have diffraction efficiency of as high as 99.9%, spectral selectivity of narrower than 20 pm (FWHM) [12], damage threshold of ~ 40 J/cm2 for ns pulses, and tolerance to CW laser radiation in near IR wavelength region of up to tens of kilowatts per square centimeter
VBGs have been successfully used for wavelength locking and spectrum narrowing of diode lasers, optical parametric oscillators, fiber lasers and solid state lasers [13]–[16]
Summary
High spectral purity and compact laser sources operating in 2 μm spectral region are of interest for a variety of applications, including medicine, LIDAR, spectroscopy, gas sensing, materials processing and various defence-related applications [1]–[4]. Conventional approaches used for achieving single longitudinal mode operation include intra-cavity etalons, twisted mode technique, unidirectional ring lasers, nonplanar ring oscillator (NPRO), and microchip lasers [5]–[9]. In terms of structure compactness, NPRO is an effective approach for achieving high power single frequency operation in isotropic host crystals [10]. Microchip laser is another compact configuration utilizing short laser gain medium and resonator length to achieve relatively large mode separation and single frequency operation [11]. Using a short cavity configuration and narrow bandwidth VBG, up to 1.4 W of single frequency output has been generated from a Tm:YAG laser at 2 m [20]. Single frequency and wavelength tunable operation of an AO Q switched Tm:YAP laser at 2 m has very recently been reported using a transversely chirped VBG, generating pulses of 230 μJ energy at 1 kHz and with a tuning range of 20 nm [22]
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