Doppler-free two-photon laser spectroscopy has been employed to measure the 12S12−22S12 transition in the muonium atom (μ+e−). A value of 2 455 529 002(33) (46) MHz has been obtained, which agrees with QED calculations within two standard deviations. The Lamb shift contributions are tested to the level 8×10−3. The corresponding measurements in hydrogen and deuterium using the same apparatus and laser system provide a test of the applied systematic corrections and have verified the systematic error of 46 MHz quoted. The mass of the positive muon has been derived from the isotope shift in this transition and yields a value of 105.65880(29)(43) MeVc2.

Peak irradiances in excess of 10(19) Wcm(-2) have been delivered to target with the VULCAN Nd:glass laser using chirped pulse amplification (CPA) [1]. Recent developments have achieved sub picosecond pulses with compressed output powers of 35 TW in a single large aperture beam, with focused intensities on target in excess of 10(19) Wcm(-2).

A measurement of the 1S-2S energy splitting by Doppler-free two-photon spectroscopy yields a value of 2 455 529 002 (33)(46) MHz, which agrees with QED theory within two standard deviations. The mass of the positive muon is derived as 105.658 80 (29) (43) MeV/c/sup 2/ from the isotope shifts in this transition to hydrogen and deuterium.<>

We report on CW quasi-phase-matched intracavity frequency doubling of a 1.064 mu m Nd:YAG laser. The 5 mm long and 0.2 mm thick crystal of periodically poled LiNbO3 was Brewster angle cut. When located intracavity, it presented an effective nonlinear coefficient d(33) of 4.5 pm/V and an estimated loss per pass less than 10%. The observed temperature bandwidth of similar to 5 K compares favourably with the theoretical value and indicates that the whole length of the crystal was contributing to the frequency doubling process.

The temporal and spectral characteristics are reported of an Er3+ -doped fibre laser incorporating frequency shifted feedback. The output of the free running laser was found to be either continuous-wave or train of driven relaxation oscillations depending on cavity loss. The performance is described and a simple theoretical model is used to predict the main features. Under cavity matching conditions, a train of pulses was generated with a repetition rate equal to the roundtrip time. Injection seeding of the laser generated a discrete comb of optical frequencies for applications in optical metrology.

A micro-fluorescence technique for profiling the spatial distribution of erbium ions doped into optical fibre preforms is reported. Profiles have been compared using fluorescence at wavelengths of 0.553 and 1.5 μm to identify a critical erbium concentration of about 0.12 wt%Er 3+ , where the effects of clustering become apparent. The addition of core co-dopants has been studied and found to have no significant effect on the active ion distribution. The variation in 1.5 μm fluorescence lifetime with position across the core has been measured. A pronounced reduction (up to 66%) in this lifetime at the core extremities was observed and indicates the presence of local ion environment disordering.

The method of Doppler-free two-photon laser spectroscopy is an ideal method for studying transitions between the 1S and 2S states in one-electron systems. An experiment at the Rutherford Appleton Laboratory has observed an unambiguous signal in the exotic muonium (mu+e-) atom. The transition frequency is DELTAnu1S-2S = 2455529002(33)(46) MHz, where the first error is of a statistical nature and the second one arises from systematic corrections, which mainly are related to the properties of the high-power pulsed laser system. There is agreement with a prior, less accurate, independent experiment at KEK and with QED theory within two standard deviations. The Lamb shift contributions are tested at the 8 x 10(-3) level. The muonium-hydrogen and muonium-deuterium isotope shifts of the 1S-2S transition have a high potential for a precise mass determination of the positive muon.

Periodic poling of z-cut lithium niobate is reliably achieved in 0.2 mm thick samples, patterned with photoresist on one face and subjected to pulsed electric fields via liquid electrodes. The acceptance bandwidth for third order second-harmonic generation reveals that the full 3.3 mm length contributes to the conversion.<>

An injection-seeded Nd: YLF laser incorporating frequency shifted feedback generates a frequency comb with a 140 GHz bandwodth and a tunable frequency spacing. Near bandwidth-limited pulses of 31 ps duration have been produced in the seeded laser by matching the frequency shift to a multiple of the cavity roundtrip frequency.

We report the operation of a laser diode pumped La1-xNdxMgAl11O19 laser mode locked by an electro-optic phase modulator. The repetition rate of the laser was 230 MHz, and the average output power was 50 mW, when pumped by a 500-mW broad-stripe laser diode. Transform-limited pulses of 14 ps duration were obtained. We have also demonstrated the FM operation of this laser, with bandwidths of up to 440 GHz being obtained.

We report the free-running and injection-seeded operation of a Nd: YLF laser incorporating frequency- shifted feedback to generate either continuous or discrete multi-frequency spectra with bandwidths up to 140 GHz (fwhm).

The development of ultrabright lasers is progressing rapidly particularly in the direction of table-top-terawatt systems operating at high pulse repetition rate with relatively low pulse energy. The highest pulse energies and highest absolute powers are being generated by the adaptation of larger-scale high energy laser systems operating in single pulse mode. The maximum focused intensity from either type of laser is determined by the beam brightness B which can be expressed in units of Watts cm-2 sterad-1. The focused intensity is then approximately B/f2 where f is the focal length to diameter ratio of the focusing optic. Brightness can be expressed as B = PS/λ2 where P is the power, λ the wavelength and S the Strehl ratio, quantifying the ratio of brightness in a beam with less than diffraction limited quality to that in a diffraction limited beam.

A novel technique for measuring the separation of widely spaced optical frequencies is demonstrated. It relies on frequency comb generation by use of a laser that incorporates a frequency-shifting element. A Nd:YLF laser is used to produce a frequency comb that has a bandwidth of 140 GHz and that contains in excess of 875 discrete frequencies, accurately spaced by 160 MHz. The longitudinal mode spacing of a dual-frequency laser was measured to an accuracy of +/-5 kHz in 3,733,440.0 kHz by use of the technique described here.

We report the generation of sub-picosecond mode- locked pulses at 1.05 μm from an additive-pulse mode- locked laser-diode-pumped La1-xNdxMgAl11O19 laser. The repetition rate was 93 MHz, and die maximum average output power was 60 mW.

Solid state lasers have undergone a renaissance since the development of reliable and cheap laser diodes which can be used as pump sources. The result is compact, efficient laser sources which are attractive for a wide range of applications. This review summarizes the properties of laser diodes which are advantageous for pumping solid state lasers and describes the diverse laser materials and configurations of solid state lasers reported in the literature.

A Ti:sapphire-pumped Nd:LMA laser has been passively mode locked by using additive-pulse mode locking, which generates 600-fs-duration pulses at 1.054 mum. The wavelength, pulse duration, and long-term stability of the laser make it eminently suitable as a front-end oscillator of a high-power, chirped-pulse amplifier experiment based on 1.053-mum amplification in Nd:phosphate glass.

We report the performance of a laser-diode-pumped Nd:glass laser. Using the AM active mode-locking technique, pulses as short as 9 ps were obtained. The development of a high power (415 mW), high optical slope efficiency (32.4%) laser-diode-pumped Nd:glass laser using high power, broad stripe laser diodes as the pump source is described. Single frequency operation of the Nd:glass laser, using an acoustooptic modulator to ensure unidirectional operation in a ring laser configuration was investigated. An instantaneous line-width of less than 300 Hz was observed.

A simple computer model of modelocking using an intracavity nonlinear mirror based on second harmonic generation has been constructed. Saturation of the gain medium is included. The model exhibits experimentally observed features such as a second harmonic conversion efficiency threshold before modelocking occurs. Self Q-switching and modelocking occurs for sufficiently large values of fluorescence lifetime. The model predicts that there is a narrow region above the modelocking threshold which allows steady state modelocking to occur even in long fluorescence lifetime materials.

We report frequency-modulation mode locking of a diode-laser-pumped Nd:glass laser. We have obtained pulses of 9-psec duration using a lithium niobate phase modulator operating at a repetition rate of 235 MHz. The average output power is 14 mW, for pumping with a 500-mW laser-diode array, and the pulses are approximately 1.4 times transform limited.