Glass Microchip Laser Research Articles

Comparison of cw laser generation in Er3+, Yb3+: glass microchip lasers with different types of glasses

AbstractThe paper describes comparison of laser generation of concentrated and SELG glasses developed at the General Physics Institute of Russian Academy of Sciences in Moscow and most recent EAT14 glass worked out by the CLaser Photonics Company in Shanghai. The laser generation was carried out using 976-nm pump wavelength in cw and quasi-cw regimes. Comparison of efficiencies and thresholds as well as of dissipative losses was made with a view to choose the best glass for “eye-safe” microchip laser range-finder. The generated wavelengths by each sample were measured.

A cobalt-doped transparent glass ceramic saturable absorber Q-switch for a LD pumped Yb3+/Er3+ glass microchip laser

We fabricate a transparent glass ceramic contains magnesium-aluminum spinel nanocrystallites doped with Co2+ ions. The ground-state and excited-state absorption cross section of this glass ceramic at 1.54 μm are estimated to be (2.8 ± 0.3) × 10−19 cm2 and (4.8 ± 0.5) × 10−20 cm2, respectively. For the first time, the passively Q-swithched operation of LD pumped 1.54 μm microchip Yb3+/Er3+ glass laser is realized with transparent glass ceramic as saturable absorber. The Q-switched pulses of 3.846 kHz in repetition rate, 6.2 ns in duration and 6.3 μJ in energy are obtained. At last, the dependences of pulse width and repetition rate on pump power are also investigated.

Effect of thermal lens on beam quality and mode matching in LD pumped Er–Yb-codoped phosphate glass microchip laser

The theoretical values of the thermal focal length and laser beam waist are derived from the theoretical model and transformation theory, respectively. The values of thermal focal length, laser beam waist and the far field divergence angle were experimentally measured in a laser diode (LD) pumped erbium–ytterbium(Er–Yb)-codoped phosphate microchip glass laser. As an extension of thermal effect studies, we investigate the role of thermal lens on beam quality and the mode matching between the pump and the laser, which affects laser efficiency in TEM00 operation. The study shows that the experimental data are in good agreement with the theoretical predictions.

Investigation of the roundtrip cavity loss in laser diode pumped erbium:ytterbium-phosphate glass microchip lasers

We present a method for determination of the roundtrip cavity loss in the laser diode pumped erbium:ytterbium-codoped phosphate glass microchip laser. Slope efficiency and laser threshold were measured in the experiment and their dependencies on roundtrip cavity loss were derived through rate equations. According to the energy levels, cumulative upconversion and cooperative upconversion are taken into consideration to ensure the accuracy of the derivation. Roundtrip cavity losses in different cavity configurations were investigated.

Model of Longitudinally Laser Diode Pumped Erbium–Ytterbium-Codoped Phosphate Glass Microchip Laser With Upconversion

A theoretical model of longitudinally laser diode (LD) pumped erbirum-ytterbium-codoped phosphate glass microchip laser that includes the influence of cooperative upconversion and cumulative upconversion effects has been developed. The analytic solution with an approximation of top-hat pump and laser profile is derived to show the influence of the both upconversions on the threshold and slope efficiency. When the Guassian profiles of both pump and oscillating lasers are considered, rigorous numerical calculations have been made to study the influence of cooperative upconversion and cumulative upconversion effects. The results of calculations are in good agreement with our experimental data. The influence of the round-trip dissipative optical loss, the waist of pump beam and the transmission on laser optimization is also discussed when considering the upconversion effects.

Determination of the thermal loading in laser-diode-pumped erbium-ytterbium-codoped phosphate glass microchip laser

The fractional thermal loading in a laser-diode-pumped erbium-ytterbium-codoped phosphate glass microchip laser is an important parameter. We have developed two methods to determine the fractional thermal loading when the laser is operating on fundamental mode. By measuring far-field divergence angles, the thermal focal length and the fractional thermal loading of a microchip TEM00 laser with a short cavity length can be calculated. The fractional thermal loading is also obtained through numerical calculations of rate equations with the consideration of upconversion processes. The results of these two methods are in good agreement.

Two-frequency Er-Yb:glass microchip laser passively Q switched by a Co:ASL saturable absorber.

Passive Q switching of a two-frequency Er3+-Yb3+:glass laser at 1.55 microm with a new Co2+:La(x)Sr(1 - x)Mg(x - y)Co(y)Al(12 - x)O19 crystal as a saturable absorber is demonstrated. We show that, with an extended cavity setup, the beat frequency between the orthogonally polarized laser eigenstates is continuously tunable by adjustment of the retardance of an intracavity birefringence. A similarly built microchip laser emits two-frequency pulses of 6-ns duration with a beat frequency of as much as 19 GHz. Moreover, two-frequency pulses at 777 nm are obtained by second-harmonic generation in a periodically poled lithium niobate crystal. Such pulses can be useful for applications such as Doppler lidar radar.

Q-switching of an Er–Yb:glass microchip laser using an acousto-optical modulator

Abstract We present a compact Q-switched Er–Yb:glass microchip laser operating at the wavelength of 1.535 μm using an acousto-optical modulator. A Q-switched peak power of 325 W with a pulse-duration of 38 ns and a pulse-to-pulse jitter of less then 10 ns was achieved. Well-controlled pulses were obtained for repetition rates up to 10 kHz while the maximum pulse energy was 12 μJ. The experimental results are compared with theoretical analysis, which shows how to optimize the laser as well as fundamental limitations.

Laser characteristics at 1535 nm and thermal effects of an Er:Yb phosphate glass microchip pumped by Ti:sapphire laser

An Er:Yb codoped phosphate glass microchip laser has been studied under pumping with a Ti:sapphire laser ranging from 945 to 990 nm. The characteristics (threshold, slope efficiency) are first described for an optimized laser. The gain spectrum is calculated for the transition 4 I 13/2→ 4 I 15/2 around 1535 nm from fundamental spectroscopic data and from experimental results. Red-shift effect on the frequency of a single mode is experimentally observed when the pump power is increased, originating from thermal effects. Temperature inside the microchip cavity and thermal expansion coefficient were determined by employing the intensity ratio of two green upconversion emission line centered at 530 and 554 nm, respectively, which quantitatively explain this red shift.

Passively Q-switched microchip laser at 15 μm

We demonstrate a compact laser source in the eye-safe wavelength regime (≈1.5 µm) that produces peak powers up to 10.6 kW at pulse durations of 0.84 ns with a repetition rate exceeding 1 kHz. An Er:Yb:glass microchip laser was passively Q-switched with a semiconductor saturable absorber mirror (SESAM). We investigated SESAM damage under Q-switching conditions and developed an improved SESAM design that can withstand microjoule pulses.

Optical parametric amplification in periodically poled KTiOPO_4 seeded by an Er–Yb:glass microchip laser

An optical parametric amplifier based on periodically poled KTiOPO(4) was used to generate 3-ns pulses at 1.544 mum . The device was pumped by a Q-switched Nd:YAG laser, and the signal output-pulse energy reached 71 muJ ; the maximum gain was 66 dB. The seed source was an Er-Yb:glass microchip laser. A theoretical fit to experimental data gave an effective nonlinear coefficient of 9.7 pm/V , close to the highest values reported for periodically poled KTiOPO(4) . Furthermore, the broad parametric gain observed could be used for broadband pulse amplification.

Existence of two coupling constants in microchip lasers

We implemented two different experimental setups to probe directly the nonlinear coupling between modes in microchip lasers. We show that, remarkably, the results can be interpreted by use of Lamb's coupling constant. In an Er, Yb:glass microchip laser, we measured C(12) = 0.80 between longitudinal modes and C(xy) = 0.95 between orthogonally linearly polarized eigenstates. The high values obtained give some physical insight into the single-frequency operation of such lasers.

Eyesafe pulsed microchip laser using semiconductor saturable absorber mirrors

We passively Q-switched a diode-pumped Er/Yb:glass microchip laser at a 1.535 μm wavelength using semiconductor saturable absorber mirrors and demonstrated pulses as short as 1.2 ns. By varying the design parameters of the saturable absorber, the pump power, and the pump spot size, we achieved repetition rates from 300 Hz to 100 kHz with pulse energies up to 4 μJ.

Polarization switching of an er :yb :cr: phosphate glass microchip laser

Abstract We show that the light of a commercially available Er : Yb :Cr :phosphate glass microchip laser end-pumped at 977 nm by an InGaAs laser diode can be switched between two linear polarization eigenstates when it is submitted to a polarized optical feedback. The flip occurs when the feedback phase is scanned by the external cavity length. In our experiments the laser diode light is confined to a fiber which is single-mode at pumping wavelength and the microchip laser operates in a single- longitudinal-and transverse mode. The microchip laser exhibits a self-pulsing behavior. Key words : Solid state laser, Optical switching, Optical polariza- tion, Microstructure, Glass, Phosphate, Feedback, Optical pumping, Experimental study. pompe et le microlaser est dgalement monomode trans- verse et longitudinal. On observe un comportement auto- impulsionnel du laser. Mots el~s : Laser solide, Commutation optique, Polarisation opti- que, Microstructure, Verre, Phosphate, R6troaction, Pompage optique, Etude exp6rimentale. Contents

High erbium content heavy metal fluoride glasses

Rare earth glasses with high doping concentrations are candidates for the production of eye-safe microchip lasers for use as transmitters and detector amplifiers in laser radar systems and as transmitters in ultrahigh data rate communication systems. Presently only low concentrations of rare earths have been incorporated into glass hosts but microchip lasers will require higher dopant concentrations in order to obtain sufficient absorption of the pump radiation. In this work, glass systems based on ZrF4 were found to be able to support dopant concentrations of ErF3 up to 18 mol%. The thermal, optical and absorption properties of these ZBEAN glasses are examined as a function of concentration.

Experimental analysis and theoretical modeling of a diode-pumped Er:Yb:glass microchip laser

A comprehensive study of a diode-pumped Er:Yb:glass microchip laser, operating at 1530-nm wavelength, is presented. The operating conditions wherein a linearly polarized, single longitudinal and transverse mode operation is achieved are indicated. An optimum pump spot size that minimizes the threshold pump power and maximizes the slope efficiency is experimentally found and theoretically justified by a space-dependent rate-equation model.

Diode-pumped microchip Er–Yb:glass laser

A single-frequency, diode-pumped, Er-Yb:glass microchip laser at a 1530-nm wavelength has been designed and operated. An output power of greater than 25 mW, a linewidth narrower than 1 kHz, and a slope efficiency of 22% have been obtained.