ABSTRACT
Gradient-index alkali borosilicate antireflection films for use in laser systems were deposited by the sol-gel process. Laser damage thresholds of these films, measured with 1.06-microm 1-nsec pulses, were four times greater than thresholds of widely used, multilayer, antireflection coatings.
ABSTRACT
Antireflective surfaces were produced on optical borosilicate glass by controlled corrosion in nearly neutral solutions. The surfaces have reflectivity below 0.1% and median threshold for laser-induced damage by 1-nsec 1.06-microm pulses of 12 J/cm(2); twice the median damage threshold of thin film antireflection coatings.
ABSTRACT
Mechanically polished fused silica surfaces were heated with continuous-wave CO(2) laser radiation. Laser-damage thresholds of the surfaces were measured with 1064-nm 9-nsec pulses focused to small spots and with large-spot, 1064-nm, 1-nsec irradiation. A sharp transition from laser-damage-prone to highly laser-damage-resistant took place over a small range in CO(2) laser power. The transition to high damage resistance occurred at a silica surface temperature where material softening began to take place as evidenced by the onset of residual strain in the CO(2) laser-processed part. The small-spot damage measurements show that some CO(2) laser-treated surfaces have a local damage threshold as high as the bulk damage threshold of SiO(2). On some CO(2) laser-treated surfaces, large-spot damage thresholds were increased by a factor of 3-4 over thresholds of the original mechanically polished surface. These treated parts show no obvious change in surface appearance as seen in bright-field, Nomarski, or total internal reflection microscopy. They also show little change in transmissive figure. Further, antireflection films deposited on CO(2) laser-treated surfaces have thresholds greater than the thresholds of antireflection films on mechanically polished surfaces.
ABSTRACT
Scandium oxide has proved to be a damage-resistant high-index material in laser coatings for use at 248 nm. The results of damage threshold measurements on laser reflectors and antireflection coatings of various designs, material combinations, and deposition temperatures are presented. The most significant effects are observed for overcoat layers on high reflectors and undercoat layers on antireflection coatings. Thresholds >6 J/cm(2) for 20 nsec pulses were observed in both cases.
ABSTRACT
A series of 4-layer silica-tantala antireflection coatings was deposited under 18 different combinations of substrate temperature (175, 250, and 325 degrees C), oxygen pressure (0.5,1.0, and 2.0 x 10(-4) Torr), and rate of deposition (1.5 and 5 A/sec). Measurements of laser-damage threshold for 1064-nm, 1-nsec pulses, average absorption, net stress, and reflectivity were then made on these coatings. Coatings deposited at the lowest temperature had the highest damage thresholds. Damage thresholds were found not to be directly related to average absorption or net stress. Coatings deposited on fused silica substrates which had been polished by a bowl-feed process had generally higher damage thresholds than coatings deposited on conventionally polished fused silica or on BK-7 glass polished by either conventional or bowl-feed processes. Baking coatings in air for 4 h at 400 degrees C generally reduced average absorption and net stress, changed the net stress from compression to tension and, in some cases, increased the damage threshold.
ABSTRACT
The design and performance of an avalanche transistor switchout are described. The device selects a single pulse from a train of cw or Q-switched mode-locked pulses and introduces less than +/-1% amplitude variation in the selected pulse. The prepulse rejection ratio exceeds 10(7), and a lifetime of greater than 10(7) shots has been achieved.
