Numerical modeling and determination of limiting powers for volume Bragg gratings used in lasers for spectral control

Tjörnhammar, Staffan; Pasiskevicius, Valdas; Laurell, Fredrik

doi:10.1364/josab.30.002326

Cited by 3 publications

(1 citation statement)

References 18 publications

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“…We chose this cavity design to avoid having the passive Q-switch exposed to pump light, to get flexibility in choosing the intensity on the Q-switch and at the same time getting a large mode size at the VBG. The latter is important as it has been previously shown that there is a limit to the amount of power a VBG can be exposed to without a decrease in its diffraction efficiency [20,21], and this limit increases linearly with the mode radius [22]. The gain medium was a 1.5-mm-long, Ng-cut Yb:KYW crystal with 5 at.% Yb-doping and both endsurfaces AR-coated for pump and emission wavelengths.…”

Section: Resultsmentioning

confidence: 99%

A frequency-locked and frequency-doubled, hybrid Q-switched Yb:KYW laser at 515 nm with a widely adjustable repetition rate

et al. 2015

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example which we have been dealing with is in vivo excitation of fluorescent proteins and specifically enhanced yellow fluorescent protein (eYFP) which has an emission cross section that is about 1.4 times higher than enhanced green fluorescent protein (eGFP) at its emission peak [1]. The goal is sufficient excitation of eYFP or the similar derivative Venus YFP [2] in order to obtain substantial stimulated emission in the environment of a living cell. These socalled living lasers have been demonstrated by employing eGFP as a molecule providing stimulated emission [3,4]. The peak excitation wavelength for the YFP family proteins is at 515 nm, accessible directly by frequency-doubled Yblasers. Continuous-wave or high-repetition-rate excitation is ruled out due to thermal cell damage and/or bleaching of the chromophore. Stable laser properties are necessary for such applications in order to maintain constant frequency conversion efficiency and a constant beam size in the excitation volume. Achieving this requires maintaining unchanged thermal conditions in the laser throughout the repetition rate tuning range. At the same time, the output wavelength has to be locked and the spectrum sufficiently narrows in order to maintain constant second harmonic generation (SHG) efficiency as the repetition rate is tuned.Here we target repetition rates from a few Hz to about 3 kHz, the upper bound limited by the radiative lifetime of the Yb 3+ excited state in Yb:KYW, and the laser material used in this work [5].There are several ways to achieve a pulsed laser source with controllable repetition rate. A seemingly simple solution for the tunable repetition rate source with stable output beam properties is an Yb-fiber amplifier seeded by an appropriate laser diode [6]. However, it is far from simple or inexpensive considering the need to effectively suppress amplified spontaneous emission and stabilize the output polarization, and it requires a laser diode which is Abstract We demonstrate a compact wavelength-stabilized, frequency-doubled Yb-doped double-tungstate laser with widely tunable repetition rate, spanning from 35 Hz to 3 kHz obtained by hybrid Q-switching. The Q-switching unit consisted of a combination of a passive Cr:YAG crystal and an opto-mechanical active intensity modulator. The fundamental wavelength was locked at 1029 nm with a volume Bragg grating, and the pulse length and energy were 42 ns and 250 µJ, respectively. As the laser was stabilized with the VBG and the opto-mechanical modulator, the frequency instability was reduced six times from free running down to 0.29 %. Frequency doubling was done extra-cavity in PPKTP, and a repetition rate-independent conversion efficiency of 63 % was obtained. The controllable repetition rate together with stable temporal and spatial characteristics makes this laser a suitable candidate in many biology-related experiments, as a pump source for in vivo excitation of fluorophores, e.g., pumping of "living lasers" and matrix-assisted laser desorption/ionization mass spectroscopy.

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Section: Resultsmentioning

confidence: 99%

A frequency-locked and frequency-doubled, hybrid Q-switched Yb:KYW laser at 515 nm with a widely adjustable repetition rate

et al. 2015

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Thermal stability of volume Bragg gratings in chloride photo-thermo-refractive glass after femtosecond laser bleaching

et al. 2018

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We demonstrate that the Joule heating of the volume Bragg grating recorded in chloride photo-thermo-refractive glass can be suppressed by bleaching the silver nanoparticles with intense ultrashort laser pulses. Measurement of the bleached grating angular selectivity showed that, at the signal wavelength at 972 nm, the spectral drift is 0.5 nm at the CW laser diode beam intensity as high as 145 W/cm. Thus, the bleaching of silver nanoparticles results in the improved thermal stability of transmission gratings, allowing one to employ them to control the powerful CW laser radiation.

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Volume Bragg Gratings - an encyclopedia article

Paschotta

2016

RP Photonics Encyclopedia

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Numerical modeling and determination of limiting powers for volume Bragg gratings used in lasers for spectral control

Cited by 3 publications

References 18 publications

A frequency-locked and frequency-doubled, hybrid Q-switched Yb:KYW laser at 515 nm with a widely adjustable repetition rate

A frequency-locked and frequency-doubled, hybrid Q-switched Yb:KYW laser at 515 nm with a widely adjustable repetition rate

Thermal stability of volume Bragg gratings in chloride photo-thermo-refractive glass after femtosecond laser bleaching

Volume Bragg Gratings - an encyclopedia article

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