Kenji Kanehara

High Peak Power, Passively

The compact (electric spark plug size), diode-pumped, passively Q-switched Nd:YAG/Cr4+:YAG microlaser was developed for ignition of engines. Output energy of 2.7 mJ per pulse and 11.7 mJ per four-pulse train with a pulsewidth of 600 ps and an M 2 value of 1.2 were obtained at a pump duration of 500 ¿s. The optical-to-optical conversion efficiency was 19%. Brightness of the microlaser was calculated as 0.3 PW/ sr-cm2 and optical power intensity was calculated as 5 TW/cm2 at the focal point of ignition. The enhanced combustion by the microlaser ignition was successfully demonstrated in a constant-volume chamber at room temperature and atmospheric pressure. The cross section area of a flame kernel generated by laser ignition is 3 times larger than that by a conventional spark plug at 6 ms after ignition in a stoichiometric mixture (A/F 15.2) of C 3H 8/air, even though ignition energy of the laser is 1/3 of that of the spark plug. Hundred percent ignition was successfully demonstrated in a lean mixture of A/F 17.2 by laser ignition, where electric spark plug ignition failed.

Q

3mJ per pulse with 1.2ns pulse width, passively Q-switched Cr:YAG/Nd:YAG micro-laser was developed for ignition of engines. The enhanced combustion by using the micro-laser igniter was successfully demonstrated in comparison with a spark plug.

-switched Microlaser for Ignition of Engines

Spark plug-size, passively Q-switched Cr:YAG/Nd:YAG micro-laser was developed for ignition of engines. Optical power intensity of >5TW/cm2 was obtained at the focal point and the enhanced combustion for leaner gas mixture was realized.

High Peak Power, Passively Q-switched Cr:YAG/Nd:YAG Micro-Laser for Ignition of Engines

Compacts, few MW-level peak power, passively Q-switched Nd:YAG/Cr4+:YAG micro-lasers with two-beam output were realized. The monolithic devices incorporate composite, all-polycrystalline ceramics components and can be used as multi-point igniters in internal combustion engines.

Compact, high peak power, passively Q-switched micro-laser for ignition of engines

The performance of a prototype micro-laser ignition system developed by DENSO was evaluated on a single cylinder natural gas research engine. Several geometric combinations of pre-chamber spacing and hole sizes were tested at two engine load conditions. Significant improvements in brake thermal efficiency (BTE) were realized due to the extension of the lean ignition limit with a slight penalty in NOx.

Composite all-ceramics, passively Q-switched Nd:YAG/Cr 4+ :YAG monolithic micro-laser with two-beam output for multi-point ignition

A 0.3PW/sr-cm2, high brightness passively Q-switched Cr:YAG/Nd:YAG micro-laser was tested for ignition of a real automobile engine. Stable engine operation was demonstrated with an ignition optical energy of 2.3mJ, lowest ever reported.