Refine
Year of publication
Document Type
- Article (31)
- Monograph/Edited Volume (5)
- Doctoral Thesis (1)
- Part of Periodical (1)
Is part of the Bibliography
- yes (38)
Institute
In side pumped laser head geometries good extraction of energy has to be weighted against diffraction effects of the amplified beam. Beam clipping at the aperture of laser rods can be avoided by using an undoped cladding around the doped core. The wings of e. g. Gaussian beams can be accommodated in the cladding. Phase distortion by the refractive index step of the rod can be compensated by a phase conjugating mirror in double pass configuration. In our proof of principle experiment the brightness of the beam from core doped amplifier rods was shown to be doubled compared to a conventional rod of the same outer diameter. (c) 2006 Optical Society of America
A frequency stabilization scheme following the Pound-Drever-Hall technique modified with a sample and hold circuit has been applied to a Q-switched diode-pumped Nd:YAG ring oscillator. The high-power ring is injection seeded by a monolithic non-planar ring laser oscillator (NPRO). The slave oscillator emits pulses of 23 ns duration and 20 mJ pulse energy with almost diffraction limited beam quality (M-2 = 1.2) at a repetition rate of 400 Hz. The short-term fluctuation of the center frequency from pulse to pulse is 290 kHz. The oscillator is designed for applications within lidar measurements.
Correlations between photons are interesting for a number of applications and concepts in metrology, in particular for resolution improvements in different methods of quantum imaging. We demonstrate the application of a blazed grating for the characterization of the degree of spatial correlation of biphotons. The biphotons are generated by type II parametric downconversion. Compared to an ordinary transmission grating, a blazed grating shows a high diffraction efficiency only for a single order of diffraction. Thus, higher intensities in the Fraunhofer far field behind the grating, and easier photon counting, can be achieved. The distribution of the two-photon rate in the Fraunhofer far field of the blazed grating can show one additional order of diffraction with a visibility related to the degree of correlation of the biphotons. The number of spatial modes that are populated by the biphoton beam can be directly altered in our experiments. The relation of the spatial mode order of the photon propagation to the observable degree of spatial correlation of the biphotons is investigated and related to the Schmidt number of spatially entangled modes.
We study thermally induced birefringence in crystalline Nd:YAG zigzag slab lasers and the associated depolarization losses. The optimum crystallographic orientation of the zigzag slab within the Nd:YAG boule and photoelastic effects in crystalline Nd:YAG slabs are briefly discussed. The depolarization is evaluated using the temperature and stress distributions, calculated using a finite element model, for realistically pumped and cooled slabs of finite dimensions. Jones matrices are then used to calculate the depolarization of the zigzag laser mode. We compare the predictions with measurements of depolarization, and suggest useful criteria for the design of the gain media for such lasers.
Q switch and longitudinal modes of a laser oscillator with a stimulated-Brillouin-scattering mirror
(1999)
We characterize the entanglement in position and momentum of photon pairs generated in type-II parametric down- conversion. Coincidence maps of the photon positions in the near-field and far-field planes are observed in two transverse dimensions using scanning fiber probes. We estimate the covariance matrix of an effective two-mode system and apply criteria for entanglement based on covariance matrices to certify space-momentum entanglement. The role of higher- order spatial modes for observing spatial entanglement between the two photons is discussed.
A pulsed, diode-laser-pumped Nd:YAG master oscillator power amplifier (MOPA) in rod geometry, frequency stabilized with a modified Pound-Drever-Hall scheme is presented. The apparatus delivers 33-ns pulses with a maximum pulse energy of 0.5 J at 1064 nm. The system was set up in two different configurations for repetition rates of 100 or 250 Hz. The beam quality was measured to be 1.5 times the diffraction limit at a pulse energy of 405 mJ and a repetition rate of 100 Hz. At 250 Hz with the same pulse energy, the M-2 was better than 2.1. The radiation is frequency converted with an efficiency of 50% to 532 nm. This MOPA system will be the pump laser of transmitters for a variety of high-end, scanning lidar systems. (C) 2005 Optical Society of America
A passively Q-switched laser with a nonlinear mirror on the basis of stimulated Brillouin scattering (SBS), generates bursts of pulses with a few 10 ns pulse duration and a separation between 20-90 mu s. Percussion drilling and trepanning are performed in different materials with 1 mm thickness. The optimum parameter set of these pulse trains with regard to the burr height and ablation rate is investigated. Differences in the processing results between single pulse and multi pulse structures are discussed. In addition the laser allowed for transiently mode locked operation. Results for mode locked and merely Q-switched operation were compared