Kunihiko Washio

Photothermal effect contribution on film quality improvement in excimer-laser induced metal CVD

KrF excimer laser induced Cr film deposition from Cr(CO)6 has been studied. Remarkable film quality dependence on laser intensity suggested the photothermal effect contribution of intensive uv laser pulses in the CVD process. A cw Ar-ion laser light and its second harmonic light were used, to separate photochemical and photothermal effects. As a result, photoinduced surface heating has been found to be very important for obtaining good quality metallic films in KrF laser induced Cr film CVD.

Laser induced metal deposition from organometallic solution

Solutions of bisbenzene metals in organic solvents have been used for the first time to produce localized deposition of metals on a glass substrate by laser induced pyrolysis. Molybdenum and chromium spots, as small as 10 μm in diameter, were obtained by using an argon‐ion laser at several tens of milliwatt power.

Generalized view of Gaussian pulse-transmission characteristics in single-mode optical fibers.

A generalized view of Gaussian pulse-transmission characteristics in single-mode optical fibers is presented. With this generalization, it becomes possible to describe manner. Gaussian pulse-transmission characteristics in a unified manner.

Stable cw backward Raman amplification in optical fibers by stimulated Brillouin scattering suppression.

A backward pumping scheme with highly repetitive short pump pulses is described for cw Raman amplification of signal light in optical fibers. This pumping scheme makes possible stable and high-gain cw Raman amplification due to the efficient suppression of stimulated Brillouin scattering, which not only limits the gain but also deteriorates the gain stability of such amplification. Stable cw backward Raman amplification of 1.4-μm laser diode light signals has been achieved, for the first time, with gains as high as 14 dB in a 5.5-μm core diam and 3.5-km long single-mode fiber, pumped with a 1.32-μm mode-locked Nd:YAG laser.

130-km-long fault location for single-mode optical fiber using 1.55-μm Q-switched Er 3+ :glass laser

An optical-time-domain reflectometer has been constructed with a 1.55-microm Er(3+):glass laser, a TeO(2) acousto-optical directional coupler, and a cooled Ge P-I-N photodiode. With it, a maximum detectable fault-location length of 130 km for single-mode optical fiber has been successfully achieved at a 1.55microm wavelength.

cw oscillation in a Nd : phosphate glass laser

A stable cw operation in a Nd : phosphate glass laser has been acheived for the first time. An end‐pumping scheme with an Ar laser in combination with a new kind of phosphate glass material has been successfully used to reduce thermal problems. More than 10 mW cw output power has been obtained in the TEM00 mode.

Output-stabilized high-repetition-rate 1.545-μm Q-switched Er:glass laser

A newly developed Q-switched Er:glass laser with a long pulse length, suitable for fiber-fault location, is described. A specially prepared athermal rod has made it possible to operate at a 5-Hz repetition rate. A feedback-stabilized Q-switching method involving fluorescence monitoring has been applied to this three-level laser system. A ±3% power stability (standard deviation) has been obtained for a 1-μsec pulse with a 2-mJ output energy.

A frequency-tunable mode-locked CW Nd:Glass laser

Mode locking and frequency tuning of a CW light-focusing Nd : glass laser called the SELFOC Nd : glass laser were achieved. Using an acoustooptic modulator having a modest degree of modulation (about 3 percent), almost perfectly mode-locked pulses as short as 49 ps were obtained. Pulsewidth was measured with an intensity-correlation method using the second-harmonic generation in KDP. Most of the observed shapes of the intensity-correlation curves were in agreement with theories previously presented by several authors. When the laser was mode locked, the long-term averaged optical spectrum was observed to narrow considerably. Some experimental evidence that the CW SELFOC Nd:glass laser could be considered to have a homogeneously broadened line was also found. Frequency tuning was achieved by using a tilted etalon in a cavity. When a 50-μm-thick etalon was used, the tuning range was more than 40 A. Pulses obtained from a frequency-tuned mode-locked laser were as short as about 100 ps.

Laser applications in the electronics and optoelectronics industry in Japan

This paper explains current status and technological trends in laser materials processing applications in electronics and optoelectronics industry in Japan. Various laser equipment based on solid state lasers or gas lasers such as excimer lasers or CO2 lasers has been developed and applied in manufacturing electronic and optoelectronic devices to meet the strong demands for advanced device manufacturing technologies for high-performance, lightweight, low power-consumption portable digital electronic appliances, cellular mobile phones, personal computers, etc. Representative applications of solid-state lasers are, opaque and clear defects repairing of photomasks for LSIs and LCDs, trimming of thick-film chip resistors and low resistance metal resistors, laser cutting and drilling of thin films for high-pin count semiconductor CSP packages, laser patterning of thin-film amorphous silicon solar cells, and laser welding of electronic components such as hard-disk head suspensions, optical modules, miniature relays and lithium ion batteries. Compact and highly efficient diode- pumped and Q-switched solid-state lasers in second or third harmonic operation mode are now being increasingly incorporated in various laser equipment for fine material processing. Representative applications of excimer lasers are, sub-quarter micron design-rule LSI lithography and low- temperature annealing of poly-silicon TFT LCD.

Negative-feedback power stabilization in a mode-locked Nd:YAG laser.

A negative-feedback laser-power control technique has been applied, for the first time known to the authors, to mode locking in a cw Nd:YAG laser, leading to great long-term stability improvement in ultrashort-pulse generation. Output-power fluctuations during the active amplitude modulation have been markedly reduced by about 20 dB. The maximum tolerable detuning range for obtaining well-stabilized output power has been extended by nearly 1 order of magnitude.