CW Laser Oscillation Research Articles

Diode pumped cw ruby laser

Cw laser oscillation of ruby at 694 nm in linear and ring resonators is reported for the first time, pumped with a 1 W laser diode at 405 nm as well as 445 nm. The ruby laser operates at room temperature with a threshold of 200 mW at 405 nm and 400 mW at 445 nm. So far output powers up to 36 mW have been achieved pumped at 405 nm. With the ruby ring laser highly coherent single frequency operation will be possible.

Highly efficient CW operation of a diode pumped Nd:Y2O3 ceramic laser

High efficiency continuous-wave laser operation of an in-house made Nd:Y2O3 ceramic was demonstrated. The Nd:Y2O3 laser ceramic was fabricated by vacuum sintering plus the hot isostatic pressing process, whose in-line transmittance reaches 81.6% at the wavelength of 1000 nm. The 1.08 and 1.36 µm CW laser oscillation of an uncoated ceramic sample was experimentally investigated. Both achieved the highest slope efficiency and output power so far reported for the Nd:Y2O3 ceramic lasers. For the operation of 4F3/2-4I11/2 transitions, simultaneous oscillations at 1074.6 nm and 1078.8 nm were observed. At an absorbed pump power of 7.0 W, a maximum output power of 3.01 W was obtained with a slope efficiency of 49.6%. For the laser operation of 4F3/2-4I13/2 transitions, a 1.68 W single wavelength at 1357.7 nm with the slope efficiency of 29.3% was achieved at the absorbed pump power of 6.7 W.

Spectral and lasing investigations of Yb:YSGG crystal

We report on a systematic study of the absorption and emission spectral properties of (Yb(0.1)Y(0.9))(3)(Sc(1.5)Ga(0.5))Ga(3)O(12) (Yb:YSGG) crystals. The broad fluorescence spectral lines indicate great potential of Yb:YSGG for tunable and ultrafast laser applications. Efficient continuous-wave (cw) laser oscillation was also demonstrated at room temperature (RT), generating an output power of 6.11 W with an optical-to-optical efficiency of 64.2%, and a slope efficiency of 80.1% with respect to absorbed pump power. The laser emission spectrum shifts to shorter wavelengths as the transmission of the output coupler varies from 3% to 20%, a result that can be explained based on the effective gain cross-sections of Yb:YSGG.

Continuous wave laser operation in Nd:GGG depressed tubular cladding waveguides produced by inscription of femtosecond laser pulses

Depressed tubular cladding waveguides have been produced in Nd:GGG crystals by using multiple inscription with femtosecond (fs) laser pulses. The guiding cores are located inside the tubular regions with cross-section diameters of 90-150 μm, which are surrounded by fs-laser induced low-refractive-index tracks. At room temperature continuous wave (cw) laser oscillations at wavelength of ~1063 nm have been realized through the optical pump at 808 nm. The slope efficiency of the cladding waveguide lasers is as high as 44.4% and the maximum output power at 1063 nm is 209 mW, which shows superior laser performance to the Type II stress induced Nd:GGG waveguides.

Continuous wave waveguide lasers of swift argon ion irradiated Nd:YVO_4 waveguides

We report on the fabrication of planar waveguide in Nd:YVO(4) crystal by using swift Ar(8+) ion irradiation. At room temperature continuous wave (cw) laser oscillation at wavelength of ~1067 nm has been realized through the optical pump at 808 nm with a low threshold of 9.3 mW. The slope efficiency of the waveguide laser system is of 8.5%. The optical-to-optical conversion efficiency is 6.6%.

Swift nitrogen ion irradiated waveguide lasers in Nd:YAG crystal

We report on the fabrication, fluorescence and laser properties of optical waveguides by swift nitrogen ion irradiation in Nd:YAG crystals. The confocal micro-luminescence investigations have concluded that the fluorescence features of the bulk material have been well preserved in the waveguide. Under 808 nm optical end-pumping, continuous-wave (cw) laser oscillation at 1064.2 nm has been demonstrated with laser slope efficiencies of 16% and pump power thresholds of 38.3 mW.

Anisotropy in laser performance of Yb:GdCa_4O(BO_3)_3 crystal

We report distinct laser performance of Yb:GdCa(4)O(BO(3))(3) crystals cut along different principal optical axes using an unpolarized diode pump. The continuous-wave (cw) laser oscillation generated with y-cut crystal is polarized either with E parallel x or with E parallel z depending on the output coupling (T) utilized; a specific T=3% leads to a special situation in which the two orthogonal polarization states coexist oscillating at different wavelengths. The laser oscillation achieved with x- and z-cut crystals is also polarized, but with a fixed polarization of E parallel z and E parallel x, respectively. The most efficient laser operation is obtained with the y-cut crystal, generating a cw output power of 7.35 W at 1083-1085 nm with an optical-to-optical efficiency of 63%, the slope efficiency being as high as 84%.

Yb‐indiffused LiNbO3 annealed/proton‐exchanged waveguide lasers

AbstractFor realization of new functionalities and exploration of application areas for LiNbO3 optical waveguide devices, rare earth element doped LiNbO3 waveguide lasers have been studied. The authors have proposed a waveguide laser using ytterbium (Yb) as the rare earth element and an annealed/proton‐exchanged waveguide as the optical waveguide. In the present research, various characteristics of the Yb:LiNbO3 needed for design and fabrication of the devices were measured. A waveguide laser was designed and fabricated and CW laser oscillation was accomplished with an Yb:LiNbO3 waveguide laser. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 90(6): 10–17, 2007; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/ecjb.20340

Tunable continuous-wave operation of a Cr^3+,Li^+:Mg_2SiO_4 laser

Room-temperature tunable cw laser oscillation of Cr3+ ions in forsterite crystals (Mg2SiO4) codoped with chromium and lithium has been demonstrated, for the first time to the authors' knowledge, in pumping a crystal with a Ti:sapphire laser into the first excited level of Cr3+ ions (4A2-4T2 transition). The laser is smoothly tunable in the region of 1095-1170 nm. A slope efficiency as great as 4.4% has been achieved.

Studies of CW laser oscillation on the 1315-nm transition of atomic iodine pumped by O/sub 2/(a/sup 1//spl Delta/) produced in an electric discharge

In this paper, we report on studies of a continuous-wave laser at 1315 nm on the I(/sup 2/P/sub 1/2/)/spl rarr/I(/sup 2/P/sub 3/2/) transition of atomic iodine where the O/sub 2/(a/sup 1//spl Delta/) used to pump the iodine was produced by a radio frequency excited electric discharge. The electric discharge was sustained in He-O/sub 2/ and Ar-O/sub 2/ gas mixtures upstream of a supersonic cavity which is employed to lower the temperature of the continuous gas flow and shift the equilibrium of atomic iodine in favor of the I(/sup 2/P/sub 1/2/) state. The results of experimental studies for several different flow conditions, discharge arrangements, and mirror sets are presented. The highest laser output power obtained in these experiments was 520 mW in a stable cavity composed of two 99.995% reflective mirrors.

Diode pumping of a continuous-wave Pr^3+-doped LiYF_4 laser

We report, for the first time to our knowledge, diode-pumped cw laser oscillation of Pr3+:LiYF4 in the red spectral range. The pump power is provided by a GaN laser diode emitting a maximum output power of 25 mW at a wavelength of approximately 442 nm. The Pr3+ laser emits 1.8 mW of output power at a 639.7-nm wavelength. Threshold pump power and slope efficiency in a nonoptimized setup are determined to be 5.5 mW and 24%, respectively.

Laser oscillation with low quantum defect in Yb:GdVO4, a crystal with high thermal conductivity.

A Yb:GdVO4 single crystal was grown by the Czochralski process. Its thermal conductivity was measured by photothermal analysis and reached 8.1 and 7.1 W m(-1) K(-1) along and perpendicular to the c axis, respectively. These values are in good agreement with the predicted ones. The optical spectroscopy of the crystal, such as its absorption and emission cross sections under the two polarizations, its fluorescence lifetime, and its laser parameters, is investigated. Cw laser oscillation is obtained for what is to our knowledge the first time in this material under titanium sapphire pumping at 984 nm. We obtain 420 mW of output power for a 2% output coupler at 1029 nm. With a thin sample, the laser wavelength decreases to 1015 nm. In this case the quantum defect is as small as 2.9%. The weak heat release of the material suggests good prospects for its use in high-power applications.

Modeling of radiation-balanced continuous-wave laser oscillators

A model has been developed to describe the dynamic behavior of radiation-balanced cw laser oscillators. We have derived algebraic equations and analytic expressions from the set of coupled rate equations and the requirements for radiation balance. The analytic expression predicts that the characteristics of a radiation-balanced laser are explicitly affected only by temperature, cavity parameters, and fundamental material properties. Several figures are generated from the derived expressions by use of Yb:KGW as an example. From these figures, the output characteristics of radiation-balanced laser oscillators are well revealed.

Highly efficient continuous-wave operation at 1030 and 1075 nm wavelengths of LD-pumped Yb3+:Y2O3 ceramic lasers

Room-temperature cw laser oscillations at 1030 and 1075 nm wavelengths were demonstrated for the TEM00 mode with Yb3+:Y2O3 ceramics by LD-pumping. A maximum extraction efficiency of 72% at 1075 nm lasing wavelengths and of 45% at 1030 nm lasing wavelengths were observed.

Neodymium doped yttrium aluminum garnet (Y3Al5O12) nanocrystalline ceramics—a new generation of solid state laser and optical materials

We have developed and adequately characterized a new generation of solid-state laser and optical materials on the basis of highly transparent nanocrystalline yttrium aluminium garnet Y3Al5O12 (YAG) ceramics. We consider this new type of inorganic laser media as an illustration of selected results of the latest investigations of laser and spectroscopic parameters of nanocrystalline Nd3+:YAG ceramics. In particular, absorption, luminescence, stimulated Raman scattering properties, as well as highly efficient CW laser oscillation at wavelength of 1064 nm under laser-diode pumping were investigated. The results show that this new laser material is a very good alternative to Nd3+:YAG single crystals. In particular, in preliminary comparison laser experiments with both Nd3+:YAG ceramic and single-crystal rods, output powers of 88 W and 99 W were obtained corresponding to optical-to-optical efficiencies of 30% and 34% for ceramic and single crystal rods, respectively. A CW 1.46 kW high power Nd:YAG ceramic laser was developed. Quite recently, laser oscillation at ≈1.32 μm was also demonstrated.

InGaAsP/InP Laterally Coupled Distributed Feedback Ridge Laser

A 1.3-µm-wavelength InGaAsP/InP laterally coupled distributed feedback ridge laser with improved structure and characteristics is reported in this paper. For easier fabrication of the first order grating with 198 nm period on and beside the ridge waveguide side-walls, two-step etching has been used to form a narrow ridge waveguide with a special shape. The grating is patterned by electron beam lithography and deeply transferred also by two-step etching, in order to enhance the lateral evanescent field coupling. A stable CW laser oscillation with a low threshold current of 17 mA at room temperature and a high side mode suppression ratio of 45 dB for a laterally coupled distributed feedback ridge laser has been achieved. An external slope efficiency of 0.25 W/A and an output power of about 25 mW are also available in our most recent devices with anti-reflection and high reflection facet coatings. The optical transmission of a Gbit/s order modulated signal has also been tested using our preliminary laser modules through a 1 km optical fiber.

Laser capabilities of CuBr mixture excited by RF discharge

Our investigations demonstrated that utilizing copper bromide (CuBr) mixture as a source of Cu atoms in a RF-excited discharge can be a promising alternative to the Cu sputtered system, when the development of Cu ion gas laser is considered. Both spectroscopic and laser investigations showed that the threshold input power for lasing was reduced about 5 times using the CuBr-based system instead of the Cu-sputtered system. Pulsed and CW laser oscillation on Cu + transitions in the near IR spectral region was obtained in RF-excited He-CuBr discharge operated at 13.56 MHz and 27.12 MHz. At input RF power of 800 W, a laser output power of 10 mW at the 780.8 nm Cu ion laser line was achieved. An increase of laser output power by a factor of two, as well as better Cu vapour axial distribution and better discharge stability, was attained when DC discharge was superimposed on the RF discharge. Laser gain on 11 UV Cu ion lines was observed in RF-excited Ne-CuBr discharge. basing on the obtained results, we consider the CuBr laser system excited by RF discharge capable of generating UV laser radiation at relatively low input power.

Er-Thermally-Diffused Ti:LiNbO3 Waveguide Laser.

An Er-thermally-diffused Ti: LiNbO3 waveguide laser was demonstrated. Er diffusion into LiNbO3 was a key process to implement the waveguide laser, and we found that thermal diffusion of an Er film of13-nm thickness at 1090°C for 100 h in dry oxygen atmosphere provides Er-diffused crystal with a smoothsurface and appropriate Er concentration. A waveguide laser was fabricated using the crystal. The waveguide laser cavity consisted of a Ti-diffused channel waveguide with 10-μm width, a dielectric mirror attached on one waveguide facet and an Au mirror deposited on the other facet. The laser was optically-pumped at 1.48-μm wavelength, and CW laser oscillation was obtained at 1.53 μm with a threshold of 10 mW. A maximum laser output up to 100 μW was obtained so far.

CW Theory of quasi-three level end-pumped laser oscillators

Equations describing the pump excitation and power extraction of end-pumped quasi-three level CW laser oscillators are derived which are useful in the optimization of such systems. The theory takes into account arbitrarily large ground state depletion due to intense pumping as well as gain saturation due to the extracting laser beam. The presented theory is more general than previously published works on the subject as it allows for the possibility of double passing the pump through the gain medium which in some instances can be an important technique for increasing system efficiency. To illustrate the utility of the derived equations, a diode end-pumped kilowatt class CW laser oscillator using Yb:YAG as the gain element is optimized and studied.

波長2.8μm固体マイクロレーザーの開発

A solid-state micro laser which has a miniature laser cavity at the end of a optical fiber has been proposed, aiming to realize a compact laser source for therapy. The micro laser will be able to deliver the laser light with around 3 μm wavelength by using conventional quartz glass optical fiber. A near infrared laser diode (LD) is used to pump the solid-state laser through the optical fiber. In this paper, LD pumped 2.8 μm cw laser oscillation is discussed A monolithic laser cavity was fabricated on a φ 2×2mm Er: YSGG crystal. A 967nm LD with optical fiber was used for pumping experiment. As a result of experiments, out put power of 160mW was obtained from the laser cavity at 950mW pumping power.