J.A. Piper

High efficiency, multi-Watt CW yellow emission from an intracavity-doubled self-Raman laser using Nd:GdVO4

Efficient multi-Watt continuous-wave (CW) yellow emission at 586.5 nm is demonstrated through intracavity frequency-doubling of a Nd:GdVO(4) self-Raman laser pumped at 880 nm. 2.51 W of CW yellow emission with an overall diode-to-yellow conversion efficiency of 12.2% is achieved through the use of a 20 mm long Nd:GdVO(4) self-Raman crystal and an intracavity mirror which facilitates collection of yellow emission generated within the resonator, and reduces thermal loading of the laser crystal.

Efficient, all-solid-state, Raman laser in the yellow, orange and red

We report efficient operation of a KGd(WO(4))(2) Raman laser pumped by a small, 1 W, 532 nm laser module. By changing the output coupler and Raman crystal orientation, more than 8 wavelengths in the yellow-to-red spectral region were generated including 555 nm, 559 nm, 579 nm, 589 nm, 606 nm, 622 nm, 636 nm and 658 nm, ie., the first 4 Stokes orders on the two orthogonal high-gain Raman shifts of KGd(WO(4))(2). We have also demonstrated spectrally pure output (typically >90% pure) for selected Stokes order with output power up to 400 mW. High slope efficiency (up to 68%) and high beam quality (M(2)~1.5) of Stokes output are obtained even at the highest pump power.

Dispersion theory of multiple-prism beam expanders for pulsed dye lasers

Abstract The single pass dispersion of multiple-prism beam expanders of interest for practical pulsed dye laser cavities is calculated. The theory is extended to enable evaluation of the overall (outward and return pass) dispersion of multiple-prism-grating combinations. It is found that although the contribution to overall dispersion from the prisms can be minimized (though not eliminated for practical expanders) by arrangement of the prisms in compensating pairs, it is in any case small (≈2%) compared to the contribution to dispersion from the grating in practical cavities. Formulae for dispersion of multiple-prism-grating combinations including up to four prisms arranged in additive or compensating configurations are given; the dispersion of an arbitrary number of prisms arranged in conjunction with a grating can also be calculated. The implications for output linewidth of pulsed dye lasers incorporating prism beam expanders are discussed.

A DOUBLE-PRISM BEAM EXPANDER FOR PULSED DYE LASERS

Abstract The design of a pulsed dye laser cavity incorporating a double-prism beam expander is described and operating characteristics compared with those of single-prism systems. Narrow spectral linewidths (δλ = 0.008 A) are achieved at relatively high efficiency (> 10%) for coumarin 500 dye solutions. Background superfluorescence in the output is low and the cavity is free from external coupling effects.

Characterising elegant and standard Hermite-Gaussian beam modes

Abstract Two tool parameters, the beam propagation factor M 2 and kurtosis factor k , are used to analyse solutions of the paraxial scalar wave equation (for rectangular coordinates) i.e. the so-called the standard and elegant Hermite–Gaussian modes (SHG and EHG). Analytical expressions for M 2 and k are derived and the correspondence between them for each form of solution is discussed in detail. These two parameters reveal information about the solutions, which leads us to derive the asymptotic representation of EHG modes (i.e. in the near-field, for a large number of modes).

Long-lived visible luminescence of UV LEDs and impact on LED excited time-resolved fluorescence applications

We report the results of a detailed study of the spectral and temporal properties of visible emission from three different GaN-based ultraviolet (UV) light emitting diodes (UV LEDs). The primary UV emission in the 360–380 nm band decays rapidly (less than 1 µs) following switch-off; however, visible luminescence (470–750 nm) with a decay lifetime of tens of microseconds was observed at approximately 10−4 of the UV intensity. For applications of UV LEDs in time-resolved fluorescence (TRF) employing lanthanide chelates, the visible luminescence from the LEDs competes with the target Eu3+ or Tb3+ fluorescence in both spectral and temporal domains. A UV band-pass filter (Schott UG11 glass) was therefore used to reduce the visible luminescence of the UV LEDs by three orders of magnitude relative to UV output to yield a practical excitation source for TRF.

Efficient all-solid-state yellow laser source producing 1.2-W average power

We report a practical and efficient all-solid-state laser source operating at 578 nm. The source comprises a diode-pumped Nd:YAG laser gain medium producing fundamental output at 1064 nm, an intracavity LiIO (3) Raman-active crystal that generates first-Stokes output at 1155 nm, and an intracavity LiB(3)O(5) frequency-doubling crystal, which frequency doubles the first-Stokes output to 578 nm. Q -switched output with as much as 1.2-W average power has been obtained; conversion efficiencies from the fundamental to the yellow as high as 33% have been obtained.

High average power, all-solid-state external resonator Raman laser

As much as 3 W of average power at 1064 nm from a diode-pumped Nd:YAG laser, Q switched at 4 kHz, was used to pump an external-resonator, crystalline Ba(NO3)2 Raman laser generating a maximum of 1.3-W output at the first Stokes wavelength of 1197 nm. The slope efficiency was 63% with respect to the fundamental power incident on the Ba(NO3)2 crystal. A reduction in the beam quality of the Stokes output from M2 approximately 1.4 at lower Stokes powers to M2 approximately 3.4 at higher powers is attributed to thermal loading of the Raman-active crystal.

Passive mode locking of a self-frequency-doubling Yb:YAl 3 (BO 3 ) 4 laser

We report passive mode-locking experiments with a novel self-doubling laser crystal Yb:YAl(3)(BO(3))(4) (Yb:YAB). The diode-pumped laser was mode locked by an ion-implanted semiconductor saturable absorber mirror. Far off phase matching, soliton mode locking produced pulse widths of 198 fs to 1.4 ps, with up to 660-mW output and optical efficiency of 24% at 1040 nm. The shortest pulses had a peak power of 28 kW with 440-mW average power and 16% efficiency. A few degrees off phase matching, a total of 60 mW of green femtosecond pulses was generated simultaneously. Close to phase matching, the laser produced picosecond pulses and, without infrared output, a total of 270 mW of green output, corresponding to 10% conversion efficiency (absorbed pump to green output).

Enhanced performance of elemental copper-vapor lasers by use of H 2 –HCl–Ne buffer-gas mixtures

The output power from a 25-mm-diameter (volume, 0.49 L) and a 40-mm-diameter (volume, 1.9 L) copper-vapor laser (nominally 20- and 65-W devices, respectively) was approximately doubled to >50 and >100 W , respectively, by addition of small partial pressures of both H(2) and HCl to the neon buffer gas. The specific output powers of these lasers are believed to be records for any copper-vapor lasers of this size.