Tunable dye laser configurations

Various configurations for the successful operation of a continuous, tunable dye laser are described. Output powers as high as 100 milliwatts have been obtained using a 1.5 watt argon ion laser at 5145 Å as the optical pump for the dye laser, with a tuning range of from 5640 Å to 6150 Å.     

Tunable distributed-feedback laser based on dye doped microporous quartz glass

The first distributed feedback (DFB) dye laser on the basis of microporous quartz glass (MQG) is reported. MQG consists of a specially processed quartz sample doped with a dye. As a pumping source a second harmonic YAG: Nd³⁺ laser with 12.5 pps repetition rate was used. Stable generation of the narrow line tuned within a spectral range of 562–584 nm and 633–663 nm with a linewidth of 0.04 nm was obtained. A high photochemical stability of the dye in the quartz matrix and reliability of MQG as an active medium for the tunable DFB laser were experimentally demonstrated.     

A high efficiency dye laser tunable from the UV to the IR

A dye laser has been developed as a source of tunable radiation in the wavelength range 3500–3700 Å. A Variety of dyes and dye mixtures have been used to cover this range. Output powers up to 30 kW are obtained with line-widths less than 1.8 Å. A Fabry-Pérot etalon reduces the output linewidth to 0.1 Å and the peak output power by a factor of three. Second harmonic powers in excess of 2 kW have been generated from the output of this laser.     

Generation of tunable subnanosecond laser pulses with a nitrogen laser pumped dye laser amplifier system

A simple method for generating single tunable subnanosecond dye laser pulses is described. A Rhodamin 6G dye laser is transversely pumped by a subnanosecond UV pulse of a TEA nitrogen laser. The narrowband output of the dye laser is amplified and shortened in a synchronously pumped amplifier. Narrowband pulses with a duration of 30–40 ps (fwhm) and a pulse power of 30 kW are obtained. They are tunable over the range of 580–600 nm.     

Shorter dye laser wavelengths from substitutedp-terphenyls

The spectral and laser characteristics of 14 CH₃-, CF₃-, and F-substitutedp-terphenyls have been investigated. 2,2″-dimethyl-p-terphenyl in cyclohexane solution exhibits a shortest tuned laser wavelength of 311.2 nm, thus extending the range of dye laser emission by 1000 cm⁻¹ in the uv. Peak output powers of 1.5 MW and 14% conversion efficiency at 332 nm were obtained under KrF-laser pumping in an untuned cavity.     

Automatic wavelength control of a flashlamp-pumped dye laser

This paper describes a technique for automatically tuning a flashlamp-pumped dye laser to the sodium D₂ line with a precision of ±2 pm (0.02 Å). The same technique could be used for tuning to other emission lines for which a monochromatic source of reasonable intensity is available. A slight modification of the method would enable the laser to be accurately tuned within a range ±10 pm (0.1 Å) of the given emission line.     

A self-quenching picosecond distributed feedback dye laser pumped by a picosecond laser pulse

A tunable single short pulse laser system with a transform–limited bandwidth pumped by a picosecond Nd:YAG laser (ca. 120 ps pulse width) is demonstrated. With this configuration, the relaxation oscillations coming from a distributed feedback dye laser cavity are completely removed. Because the pumping pulsewidth is shorter than the lifetime of dye molecule on the upper laser state, the gain of the laser medium is depleted by the first pulse. The laser wavelength could be precisely tuned with the transform-limited bandwidth (for example, a linewidth of 0.02 nm). After amplification, we obtain a single short laser pulse energy up to 500 μJ at the pulsewidth of 8.2 ps.     

Pulse properties of a synchronously mode-locked,cavity dumped,picosecond dye laser system

A synchronously mode-locked, cavity-dumped picosecond dye laser is described. The structure and intensity of the picosecond pulses measured under different conditions are reported. It was found that the structure of the pulses from the synchronously pumped dye laser depends critically on the length of the Ar⁺ laser pulses. At the shortest Ar⁺ laser pulses of about 70 ps the dye pulses are as short as 1.1 ps. With Ar⁺ laser pulses of 200 ps the dye laser pulses contains a broad satellite pulse which contains a large fraction of the total intensity. When a cavity dumper is added to the system one gets dye laser pulses 15–20 ps long with a substructure, which indicates incomplete mode-locking. Well mode-locked 1.5–2.0 ps pulses were obtained in the red part of the dye laser action spectrum, i.e. 620–650 nm for R6G, 595–608 nm for R 110 and 657–662 nm for RB, respectively. Addition of mode-locking dyes also improved the pulse quality at some wavelengths.     

Operation of a high power,broadly tunable infrared dye laser

We discuss the operation and performance of a ruby pumped infrared dye laser with a wide tuning range and a high out-put power. The longitudinally pumped infrared laser was operated in the Littrow configuration without an intracavity beam expander. The dye, IR 125, exhibited a tunability range that extended from 8325 Å to 9375 Å. The dye laser had a pulse duration of 20 ns and an output power of 12.5 MW with a 2.3 joule ruby pump. The maximum output power of the infrared laser was limited by the damage threshold of the tuning element.     

A microchip-laser-pumped DFB-polymer-dye laser

A miniaturized, high repetition rate, picosecond all solid state photo-induced distributed feedback (DFB) polymer-dye laser is described by applying a passively Q-switched and frequency-doubled Cr⁴⁺:Nd³⁺:YAG-microchip laser (pulse width Δτ=540 ps, repetition rate ν=3 kHz, pump energy E_pump=0.15 μJ) as a pump source. A poly-methylmethacrylate film doped with rhodamine B dye serves as active medium. The DFB-laser pulses are temporally and spectrally characterized, and the stability of the thin polymer/dye film at high repetition rates is analyzed. The shortest DFB-laser pulses obtained have a duration of 11 ps. After the emission of 350000 pulses the intensity of the DFB-laser output has decreased by a factor of two and the pulse duration has increased by a factor of 1.2. For single DFB-laser pulses of 20-ps duration the spectral bandwidth is measured to be Δλ=0.03 nm, which is only 0.005 nm above the calculated Fourier limit assuming a Gaussian profile for the temporal shape of the pulses. Coarse wavelength tuning of the DFB laser between 590 and 619 nm is done by turning the prism. Additionally, a fine tuning of the DFB-polymer-laser wavelength is achieved by changing the temperature of the polymer/dye layer (=-0.05 nm/°C) in the range from 20 to 40 °C. Received: 1 March 2001 / Revised version: 23 May 2001 / Published online: 18 July 2001     

A study on the control of dye solution temperature on the line-width and wavelength stability of a copper vapour laser pumped single mode dye laser

This paper presents a study on the line-width and wavelength stability of a single mode narrow line-width (≈ 100 MHz) dye laser pumped by a copper vapour laser, with and without precision temperature control of dye solution. The single mode dye laser system was based on a specially designed SS metal dye cell and grazing incidence grating (GIG) dye resonator with intra-cavity double prism beam expander and etalon. A high precision wavelength-meter was used to record the line-width and frequency stability data. With the coarse dye solution temperature control of 23 ± 2 °C, dye laser line-width varied in a periodic fashion (in every 30 s) between 100 and 770 MHz. Frequency stability was ± 215 MHz (1 min). This is attributed to switching from single to double mode due to temperature induced cavity length change. For the precise dye solution control of 23 ± 0.1 °C, the periodic variation of the line-width was removed completely and the line-width was always ≤ 100 MHz. The frequency stability also improved to ± 42 MHz (1 min). It is established that the dye temperature control is very crucial for achieving, highly frequency stable single axial mode operation.     

Physics and technology of tunable pulsed single longitudinal mode dye laser

Design and technology demonstration of compact, narrow bandwidth, high repetition rate, tunable SLM dye lasers in two different configurations, namely Littrow and grazing incidence grating (GIG), were carried out in our lab at BARC, India. The single longitudinal mode (SLM) dye laser generates single-mode laser beams of ∼400 MHz (GIG configuration) and ∼600 MHz (Littrow configuration) bandwidth. Detailed performance studies of the Littrow and GIG dye laser resonators showed that GIG dye laser results in narrower linewidth and broad mode hop free wavelength scanning over 70 GHz. In this paper we present experimental studies carried out on the high repetition rate SLM dye laser system.     

Phase conjugation in potassium vapour using subnanosecond laser pulses

Phase conjugated waves (PCW) were generated for the first time by degenerate four-wave mixing with subnanosecond laser pulses in potassium vapour near the D ₁ transition at 7699 Å. The light source was a long cavity grazing incidence dye laser. The pulses had a duration of 700–800 ps and a linewidth of 0.2 Å. The experiments were performed in a temperature range of 400–550° C. A maximum reflectivity of 57% has been observed together with temporal pulse shortening. PCW reflectivity has been measured as a function of the temperature, and the backward pump intensity.     

A broadly tunable IR waveguide Raman laser pumped by a dye laser

Design and performance characteristics of a tunable ir waveguide Raman laser pumped by a high power dye laser are described. Using SRS up to third Stokes order in compressed H₂, the wavelength range from 0.7 to 7 μm has been covered without gaps. Taking advantage of a waveguide structure in the scattering chamber, energy conversion efficiencies better than 1% with power levels in excess of 80 kW for the third Stokes component have been achieved. The experimental results support the theoretical predictions that a 4-wave parametric process is responsible for the production of the third Stokes component.     

New efficient laser dye for pulsed and CW operation in the UV

A new laser dye for pulsed and cw operation has been synthesized which can be tuned from 362 nm up to 412 nm. For pulsed excitation with a XeCl excimer laser an energy conversion of 18.5% has been measured at the tuning maximum of the dye; this is the highest efficiency for any known dye in the UV. For cw operation a low laser threshold and a goof efficiency have been observed. The range of tuned cw dye lasers is extended by 30 nm to shorter wavelengths. The dye shows high photochemical stability even at high pump laser power.     

CVL-pumped dye laser for spectroscopic application

A spectroscopic dye laser system-pumped by a Copper Vapor Laser (CVL)-has been built and optimized for different dye solutions operating in the spectral range from 530 to 890 nm. Conversion efficiencies up to 40% were reached in broad band operation, 24% with a prism expander grating cavity, and 20% in grazing incidence configuration, which operated at typical band widths of 3 GHz. Second harmonic generation (SHG) of the dye laser output produced tunable uv-radiation between 260 and 408 nm at conversion efficiencies 5%. Fundamental and SHG output were used for resonant ionization experiments in molecular beams.     

A novel pumping arrangement for tunable single picosecond pulse generation with a N2 laser pumped distributed feedback dye laser

A novel excitation scheme for a N₂ laser pumped distributed feedback dye laser is described. The dye laser generates 80–100 ps pulses with a time-bandwidth product better than 0.6. Several tuning methods are proposed, and a number are investigated experimentally. Continuous tuning over a 50 Å range without mode-hopping is demonstrated.     

A grating tuned cw dye laser

We report on the operation of a rhodamine 6G cw dye laser involving a simple tuning mechanism capable of achieving high output powers (～500 mW) and resolving power (0.004 nm) close to the Doppler limit for a range of light gases. The system employs a 600 line/mm diffraction grating external to, but coupled with a high Q laser cavity; continuous tuning over 50 nm of the fluorescence spectrum of the dye was obtained.     

Comparative laser performances of pyrromethene 567 and rhodamine 6G dyes in copper vapour laser pumped dye lasers

Narrowband laser performances and photochemical stability of alcoholic solutions of pyrromethene 567 and rhodamine 6G dyes, under high-repetition rate copper vapour laser (at 510 nm), as well as, high-peak intensity Nd:YAG laser (at 532 nm) excitation have been investigated. We have observed that pyrromethene 567 dye solutions offer higher efficiency, wider tuning range, but lower photochemical stability and higher lasing threshold than that of rhodamine 6G dye solutions. An addition of about 100 mM DABCO, as a singlet oxygen quencher, in pyrromethene 567 dye solutions improved its photochemical stability close to that of rhodamine 6G. The observation of higher slope efficiency, in spite of higher threshold pump energy for pyrromethene 567 dye than that of rhodamine 6G dye solutions, was explained by a predictive model on gain characteristics of both dye solutions as a function of pump energy. PACS 42.55.Mv; 42.55.Rz; 42.70.Hj; 42.70.Jk     

The effect of varying the hydraulic parameters of a flow cell in a dye laser pumped by a copper vapor laser

A simple method for measuring hydrodynamic parameters that influence the copper vapor laser (CVL) pumped dye laser stability is reported. A specially designed converging diverging curved flow duct is employed. The flow gap at the laser pump region is varied from 0.4 to 0.6 mm and the Reynolds number is varied from 1000 to 20,000. As a result, the channel aspect ratio and effective curvature ratio are varied from 41.6 to 62.5, and 69 to 102, respectively, at the CVL pump region. The variation in the intensity of a He-Ne laser beam transmitted through the water flowing in the test dye cell at different flow rates correlated with the numerically estimated hydrodynamic parameters. The impacts of these hydrodynamic parameters on a 5.5 kHz CVL pumped dye laser output are discussed.