Experimental analysis of emission linewidth narrowing in a pulsed KGd(WO4)2 Raman laser

The linewidth of a KGd(WO4)2 (KGW) intracavity pumped Raman laser is analyzed experimentally for different configurations of the Raman and pump laser resonators: with narrow and broadband pump emission profiles, with and without linewidth narrowing elements in the Raman laser resonator, with and without injection seeding into the Raman cavity. The benefits of a narrow linewidth pump source in combination with linewidth narrowing elements in the Raman laser cavity for the efficient linewidth narrowing of the Raman laser emission are explained. 20 kW peak-power pulses at 1156 nm with 0.43 cm-1 emission linewidth are demonstrated from an injection seeded KGW Raman laser

Optical gain in NV- colour centres for highly-sensitive magnetometry : a theoretical study

Optical gain in an amplifier based on NV- colour centres (CC) in diamond is proposed as a new method for optical magnetic field detection. An analytical expression for magnetic field sensitivity with this method is deduced. The sensitivity is highest at the pump intensities about 100 times above the saturation intensity of NV- CC and can reach values of ~1.4 fT/√Hz in a pump-probe configuration with NV- CC concentration in diamond of 2.5 ppm. Collection efficiency of probe emission can be simpler and significantly higher than that of NV- CC luminescence, used for conventional optical magnetometry in diamond. This makes this method attractive for applications requiring remote magnetic field sensing

Optical trapping with "on-demand" two-photon luminescence using Cr:LiSAF laser with optically addressed saturable Bragg reflector

We demonstrate a diode-pumped Cr:LiSAF laser with controllable and reliable fast switching between its continuous-wave and mode-locked states of operation using an optically-addressed semiconductor Bragg reflector, permitting dyed microspheres to be continuously trapped and monitored using a standard microscope imaging and on-demand two-photon-excited luminescence techniques

Characterization of single-crystal synthetic diamond for multi-watt continuous-wave Raman lasers

A continuous-wave diamond Raman laser is demonstrated with an output power of 5.1 W at 1217 nm. This Raman laser is intracavity pumped by a side-pumped Nd:YLF rod laser: a 43-fold brightness enhancement between the Nd:YLF and diamond Raman lasers is observed, with the M2 beam propagation factor of the diamond Raman laser measured to be <; 1.2. Although higher output powers are demonstrated in a similar configuration using KGd(WO4)2 (KGW) as the Raman laser material (6.1 W), the brightness enhancement is much lower (2.5 fold) due to the poorer beam quality of the KGW Raman laser (M2 <; 6). The Raman gain coefficient of single-crystal synthetic diamond at a pump wavelength of 1064-nm is also measured: a maximum value of 21±2 cm/GW is returned compared to 5.7±0.5 cm/GW for KGW at the same wavelength

Steady-state Raman gain in diamond as a function of pump wavelength

The variation in the Raman gain coefficient in single-crystal diamond for pump wavelengths between 355 and 1450 nm is measured. Two techniques are used: a pump-probe approach giving an absolute measurement and a stimulated Raman oscillation threshold technique giving a relative measurement. Both approaches indicate that the Raman gain coefficient is a linear function of pump wavenumber. With the pump polarized along a direction in the crystal, the Raman gain coefficient measured by the pump-probe technique is found to vary from 7.6 +/- 0.8 for a pump wavelength of 1280 nm to 78 +/- 8 cm/GW for a pump wavelength of 355 nm. With the established dependence of the Raman gain coefficient on the pump wavelength, the Raman gain coefficient can be estimated at any pump wavelength within the spectral range from 355 up to 1450 nm

100 kW peak power external cavity diamond Raman laser at 2.52 μm

We report an external cavity diamond Raman laser operating at 2.52 μm, pumped by a 1.89 μm Tm:LiYF4 (YLF) laser. The maximum pulse energy at 2.52 μm is 1.67 mJ for 4.4 mJ of pump, yielding a conversion efficiency of 38 %. The best slope efficiency is ~60% and the Raman pulse duration is between 11 and 15 ns for ~33 ns pump pulse duration. The peak power at 2.52 μm is >100 kW. This demonstration of a Thulium laser pumped diamond Raman laser paves the way for accessing the industrially important wavelength region of ~2.5 μm

Sub-100 ps monolithic diamond Raman laser emitting at 573 nm

We report a compact and efficient picosecond diamond Raman laser at 573 nm wavelength. The laser consists of a 0.5 mm thick single-crystal synthetic diamond coated to form a plane–plane laser resonator, and pumped at 532 nm by a frequency-doubled Q-switched microchip laser system. The pump delivers 85 ps pulses at 100 kHz repetition rate at a maximum average power of ~500 mW. We demonstrate 1st Stokes emission from the diamond Raman laser with maximum power of 175 mW, corresponding to a conversion efficiency of 47% and a pulse duration of 71 ps. Substantial pulse shortening is obtained by proper adjustment of the pump spot diameter on the diamond sample. A minimum pulse duration of 39 ps is reported for a conversion efficiency of 36% and 150 mW output power. The simplicity of the architecture makes the system highly appealing as a yellow picosecond laser source

Space Object Identification and Classification from Hyperspectral Material Analysis

This paper presents a data processing pipeline designed to extract information from the hyperspectral signature of unknown space objects. The methodology proposed in this paper determines the material composition of space objects from single pixel images. Two techniques are used for material identification and classification: one based on machine learning and the other based on a least square match with a library of known spectra. From this information, a supervised machine learning algorithm is used to classify the object into one of several categories based on the detection of materials on the object. The behaviour of the material classification methods is investigated under non-ideal circumstances, to determine the effect of weathered materials, and the behaviour when the training library is missing a material that is present in the object being observed. Finally the paper will present some preliminary results on the identification and classification of space objects.Comment: 30 pages, 24 figure

Intracavity Raman conversion of a red semiconductor disk laser using diamond

We demonstrate a diamond Raman laser intracavity-pumped by a red semiconductor disk laser (~675 nm) for laser emission at around 740 nm. Output power up to 82 mW of the Stokes-shifted field was achieved, limited by the available pump power, with an output coupling of 1.5%. We also report wavelength tuning of the diamond Raman laser over 736 - 750 nm

1.6 W continuous-wave Raman laser using low-loss synthetic diamond

Low-birefringence (Δn<2x10−6), low-loss (absorption coefficient <0.006cm−1 at 1064nm), single-crystal, synthetic diamond has been exploited in a CW Raman laser. The diamond Raman laser was intracavity pumped within a Nd:YVO4 laser. At the Raman laser wavelength of 1240nm, CW output powers of 1.6W and a slope efficiency with respect to the absorbed diode-laser pump power (at 808nm) of ~18% were measured. In quasi-CW operation, maximum on-time output powers of 2.8W (slope efficiency ~24%) were observed, resulting in an absorbed diode-laser pump power to the Raman laser output power conversion efficiency of 13%