Continuous-wave broadly tunable Cr:ZnSe laser pumped by a thulium fiber laser

We describe a compact, broadly tunable, continuous-wave (cw) Cr²⁺:ZnSe laser pumped by a thulium fiber laser at 1800 nm. In the experiments, a polycrystalline ZnSe sample with a chromium concentration of 9.5 × 10¹⁸ cm⁻³ was used. Free-running laser output was around 2500 nm. Output couplers with transmissions of 3%, 6%, and 15% were used to characterize the power performance of the laser. Best power performance was obtained with a 15% transmitting output coupler. In this case, as high as 640 mW of output power was obtained with 2.5 W of pump power at a wavelength of 2480 nm. The stimulated emission cross-section values determined from laser threshold data and emission measurements were in good agreement. Finally, broad, continuous tuning of the laser was demonstrated between 2240 and 2900 nm by using an intracavity Brewster cut MgF₂ prism and a single set of optics.     

Broadly tunable continuous-wave diode-pumped Cr4+:YAG laser

We describe a widely tunable, continuous-wave, room temperature Cr⁴⁺:YAG laser with direct pumping by two high brightness 4 W InGaAs laser diodes. In a tunable configuration, the output wavelength covered a span of 197 nm (1356–1553 nm) and provided a maximum power of 195 mW. A maximum non-tunable output power of 260 mW was obtained with a 0.6% transmission output coupler (OC) and 6.6 W of incident pump power. Pumping at two different wavelengths, 911 and 968 nm, was investigated.     

Spectral kinetic properties and lasing characteristics of diode-pumped Cr<Superscript>2+</Superscript>:ZnSe single crystals

The temperature and concentration quenching of the luminescence of Cr²⁺ ions in Cr:ZnSe crystals is experimentally investigated and the radiative lifetime of the upper lasing level is determined. The values of the cross sections of absorption from the ground state of Cr²⁺ ions in Cr:ZnSe crystals are refined. It is shown that the absorption from the excited state of Cr²⁺ ions is negligible near 1.5 μm. Lasing in Cr:ZnSe single crystals is implemented with an efficiency of 31% and an output power of 186 mW using laser diode pumping at a wavelength of 1.77 μm.     

Tunable,narrow linewidth,linearly polarized and gain-switched Cr<Superscript>2+</Superscript>:ZnSe laser

We demonstrate a tunable, narrow linewidth, linearly polarized and gain-switched Cr²⁺:ZnSe laser pumped by a Tm, Ho:YVO₄ laser at 10 kHz pulse repetition frequency. By setting a quartz birefringent filter with a Brewster angle in the cavity, the linearly polarized Cr²⁺:ZnSe laser can be continuously tuned from 2.45 to 2.50 μm, and the output power was almost not changed. In addition, the linewidth was compressed to about 5 nm. At the incident pump power to the crystal of 14 W, the maximum output power of 2.84 W was obtained, corresponding to a slope efficiency of 20.4%.     

Comparison of RTP electro-optic Q-switch and acousto-optic Q-switch in Tm,Ho:GdVO<Subscript>4</Subscript> laser

We demonstrate a tunable, narrow linewidth, linearly polarized and gain-switched Cr²⁺:ZnSe laser pumped by a Tm, Ho:YVO₄ laser at 10 kHz pulse repetition frequency. By setting a quartz birefringent filter with a Brewster angle in the cavity, the linearly polarized Cr²⁺:ZnSe laser can be continuously tuned from 2.45 to 2.50 μm, and the output power was almost not changed. In addition, the linewidth was compressed to about 5 nm. At the incident pump power to the crystal of 14 W, the maximum output power of 2.84 W was obtained, corresponding to a slope efficiency of 20.4%.     

Continuous-wave tunable Cr2+:ZnS laser

We report the first continuous-wave tunable over ∼280 nm around 2.3 μm room-temperature operation of a chemical vapor transport-grown and diffusion-doped Cr²⁺:ZnS laser, pumped by a Co:MgF₂ laser at 1.67 μm and generating over 100 mW of output power at 16% slope efficiency. The self-consistent results of the laser and spectroscopic analysis demonstrate a large potential of this crystal as an active medium for diode-pumped tunable mid-infrared sources. Received: 7 January 2002 / Revised: 14 March 2002 / Published online: 2 May 2002     

Characteristics of Nd：GdVO4 Laser with Different Nd-Doping Concentrations

We report the properties of a compact diode-pumped continuous-wave Nd：GdV04 laser with a linear cavity and different Nd-doped laser crystals. In a 0.2at.% Nd-doped Nd：GdVO4 laser, 1.54 W output laser power is achieved at 912nm wavelength with a slope efficiency of 24.8% at an absorbed pump power of 9.4W. With 0.3at.% Nd-doping concentration, we can obtain the either single-wavelength emission at 1064nm or 912nm or the dual-wavelength emission at 1064nm and 912nm by controlling the incident pump power. From an incident pump power of 11.6 W, the 1064nm emission between ^4Fa/2 and ^4I11/2 is suppressed completely by the 912nm emission between ^4Fa/2 and ^4I9/2. We obtain 670 mW output of the 912nm single-wavelength laser emission with a slope efficiency of 5.5% by taking an incident pump power of 18.4 W. Using a Nd：GdV04 laser with 0.4at.% Nd-doping concentration, we obtain either the single-wavelength emission at 1064nm or the dual-wavelength emission at both 1064nm and 912nm by increasing the incident pump power. We observe a strong competition process in the dualavelength laser.     

Low-threshold, 12-MHz, multipass-cavity femtosecond Cr4+: Forsterite laser

We report on the development of an extended-cavity, low-threshold femtosecond Cr⁴⁺:forsterite laser operating near 1270 nm. The resonator was end-pumped by a continuous-wave Yb-fiber laser at 1060 nm. The 195-MHz short cavity could be operated with absorbed threshold pump powers as low as about 300 mW. To scale up the pulse energy, the cavity length was increased by using a q-preserving multipass cavity (MPC) consisting of a flat and a curved (R = 4 m), notched high-reflector. Kerr-lens mode locking was used to generate femtosecond pulses and double-chirped mirrors were included in the cavity for dispersion compensation. With an absorbed pump power of 1250 mW, the mode-locked laser produced 4 nJ of pulse energy at an average output power of only 47 mW. The corresponding repetition rate of the extended cavity was 11.7 MHz. The pulse-width was 90 fs and the spectral bandwidth was 23 nm, corresponding to a time-bandwidth product of 0.37.     

Self-starting five optical cycle pulse generation in Cr<Superscript>4+</Superscript>:YAG laser

We report stable self-starting near-transform-limited 26-fs pulses at 250-mW output power from a Kerr-lens mode-locked (KLM) Cr⁴⁺:YAG laser using chirped mirrors in combination with prisms. The highest output power achieved in KLM regime was 600 mW at 55-fs pulse duration. The experimental results agree well with the results of theoretical analysis with respect to KLM self-starting ability and stability against continuous-wave and multi-pulse operation. Parameter ranges for stable transform-limited KLM pulses as well as the shortest achievable pulse durations are established. Using an InGaAs-InP semiconductor saturable absorber mirror we could obtain self-starting 57-fs pulses at the average output power of 200 mW. Two-photon absorption was found to be the main mechanism favoring the multiple-pulse operation. Received: 2 May 2002 / Revised version: 16 July 2002 / Published online: 8 January 2003 RID="*" ID="*"Corresponding author. Fax: +43-1/58801-38799, E-mail: sorokina@tuwien.ac.at     

Low-cost low-threshold diode end-pumped Tm:YAG laser at 2.016?μm

We report a low-threshold continuous-wave Tm:YAG laser that can be excited near 785?nm with low-cost, single-mode AlGaAs laser diodes. Low-threshold operation was achieved using a tightly focused, astigmatically compensated x-cavity containing a 2-mm-thick Tm:YAG crystal with 5?% Tm³⁺ concentration. Two linearly polarized single-mode diodes operating at 785.8?nm were polarization coupled to end pump the resonator. With a 6?% output coupler, as high as 32?mW of output power could be obtained at 2016?nm with 184?mW of incident pump power. The output could be further tuned in the 1935?C2035?nm range. Slope efficiency measurements indicated that cross-relaxation was very effective at this doping level. With a 2?% output coupler, lasing could be obtained with as low as 32.3?mW of pump power. In the limit of vanishing output coupling, the incident threshold pump power could be reduced to as low as 25?mW. To our knowledge, this is among the lowest lasing thresholds reported to date for continuous-wave, room-temperature thulium lasers.     

1.9- m and 2.0- m laser diode pumping of Cr(2+) :ZnSe and Cr(2+) :CdMnTe

Efficient diode pumping at wavelengths of 1.9 and 2.0microm of a Cr(2+): ZnSe laser with an output power of 105 mW and a slope efficiency of 35% with respect to the absorbed pump power is presented. In addition, Cr(2+): CdMnTe has been laser diode pumped as well as operated in the continuous-wave regime, to the best of our knowledge for the first time.     

Dual-wavelength laser operation at 1061 and 942 nm in Nd:GSAG

A dual-wavelength continuous-wave (CW) diode end-pumped gadolinium scandium aluminum garnet (Nd:GSAG) laser that generates simultaneous laser action at the wavelengths 1061 and 942 nm is demonstrated. A total output power of 589 mW (476 mW at 1061 nm and 113 mW at 942 nm) for the dual-wave-length was achieved at the incident pump power of 18.2 W. The M ² values for 942 and 1061 nm lights were found to be around 1.18 and 1.37, respectively.     

Diode-pumped continuous-wave Nd<Superscript>3+</Superscript>:YAlO<Subscript>3</Subscript> intracavity-doubled red laser

It is reported that efficient continuous-wave (CW) red laser generation at 670 nm in a LBO crystal at type-I phase matching direction performed with a diode-pumped Nd³⁺:YAlO₃ (Nd:YAP) laser. With incident pump power of 15.6 W, output power of 273 mW at 670 nm has been obtained using a 10 mm-long LBO crystal. At the output power level of 273 mW, the output stability is better than 3.7%.     

Diode-Pumped Nd:CNGG-LBO CW sum-frequency mixing blue-green laser at 497 nm

We report for the first time a continuous-wave (CW) blue-green laser emission by sum-frequency mixing in Nd:CNGG crystal. Using type-I critical phase-matching LBO crystal, a blue-green laser at 497 nm is obtained by 1061 and 935 nm intracavity sum-frequency mixing. The maximum laser output power of 232 mW is obtained when an incident pump laser of 18.2 W is used. At the output power level of 232 mW, the output stability is better than 3.67%. The beam quality M ² value is are about 1.26 and 1.38 in both horizontal and vertical dimensions respectively.     

Diode pumped Pr<Superscript>3+</Superscript>:LiYF<Subscript>4</Subscript>-BBO ultraviolet laser at 320 nm

A diode pumped Pr³⁺:LiYF₄ laser at 639.5 nm has been demonstrated. With an incident pump power of 920 mW, the maximum red output power was 272 mW. Moreover, intracavity second-harmonic generation (SHG) has also been achieved with a maximum ultraviolet power of 23 mW by using a β-BaB₂O₄ (BBO) nonlinear crystal. To the best of our knowledge, this is the first report on continuous-wave ultraviolet generation by intracavity frequency doubling Pr³⁺:LiYF₄ laser.     

Dual-wavelength Nd:YAP laser at 930 and 1341 nm and sum-frequency mixing for an emission at 549 nm

A dual-wavelength continuous-wave (CW) diode end-pumped Nd³⁺:YAlO₃ (Nd:YAP) laser that generates simultaneous laser action at the wavelengths 930 and 1341 nm is demonstrated. A total output power of 778 mW for the dual-wavelength was achieved at the incident pump power of 17.8 W. Furthermore, intracavity sum-frequency mixing at 930 and 1341 nm was then realized in a LBO crystal to reach the yellow-green range. We obtained a total CW output power of 103 mW at 549 nm.     

Intracavity sum-frequency generation of CW blue light in Nd:LuVO<Subscript>4</Subscript> laser

We report for the first time a continuous-wave (CW) blue laser emission by sum-frequency mixing in Nd:LuVO₄ crystal. Using type-I critical phase-matching (CPM) LBO crystal, a blue laser at 493 nm is obtained by 1066 and 916 nm intracavity sum-frequency mixing. The maximum laser output power of 520 mW is obtained when an incident pump laser of 18.2 W is used. At the output power level of 520 mW, the output stability is better than 2.8%. The beam quality M ² value is are about 1.22 and 1.31 in both horizontal and vertical dimensions respectively.     

All-solid-state Yb:KYW-LBO blue-green laser at 500 nm

It is reported that efficient continuous-wave (CW) blue-green laser generation at 500 nm in a LBO crystal at type-I phase matching direction performed with a Ti:sapphire laser-pumped Yb:KYW laser. With incident pump power of 8.7 W, output power of 138 mW at 500 nm has been obtained using a 10 mm-long LBO crystal. At the output power level of 138 mW, the blue-green output stability is better than 2.8%. The blue-green beam quality M ² values were equal to 1.25 and 1.18 in X and Y directions, respectively.     

Efficient intracavity second-harmonic generation at 930 nm in a BiB<Subscript>3</Subscript>O<Subscript>6</Subscript> crystal

It is reported that efficient continuous-wave (CW) blue laser generation at 465 nm in a BiB₃O₆ (BiBO) crystal at type-I phase matching direction performed with a diode-pumped Nd³⁺:YAlO₃ (Nd:YAP) laser. With incident pump power of 18.4 W, output power of 823 mW at 465 nm has been obtained using a 10 mm-long BiBO crystal. At the output power level of 823 mW, the output stability is better than 2.3%.     

Diode-pumped Nd:YCOB self-frequency-doubling red laser at 666 nm

It is reported that efficient continuous-wave (CW) self-frequency-doubling red laser at 666 nm performed with a diode-pumped Nd³⁺:YCa₄O(BO₃)₃ (Nd:YCOB) laser. With a diode pump power of 14.3 W, TEM₀₀ mode red laser at 666 nm of 570 mW is obtained. At the output power level of 570 mW, the output stability is better than 3.5%. The beam quality M² value is about 1.25. To the best of our knowledge, this is the highest power laser at 666 nm generated by self-frequency doubling of a diode pumped Nd:YCOB laser.