Fig. 4-6 All-solid-state (1 J) green Nd:YAG laser system

This picture, 32KB

Fig. 4-7 Schematics of the LD pumped zigzag slab Nd:YAG laser system LD pumped zigzag slab Nd:YAG crystals are used in an oscillator, a preamplifier, and two postamplifiers. An LBO crystal is used for frequency conversion.

Ti:sapphire crystal emits all the excitation energy within several tens of femtoseconds (10-15 s) and is expected to play an important role in developing an ultrahigh power laser system which would have a major impact on various fields of science and industry. Ti:sapphire is excited by green light and oscillates at a wavelength of about 800 nm. JAERI succeeded recently in developing a compact all-solid-state laser system with a high repetition rate and a high average power, which is suitable to pump ultrashort pulse, high-average power Ti:sapphire laser (Fig. 4-6). For optical pumping of Ti:sapphire until now, infrared light from Nd:YAG crystals excited by Xe-flash lamps or discharge tubes has been used after frequency conversion to obtain green light. However, the conversion efficiency and the repetition rate are low because only a small portion of the injected light is absorbed by Nd3+ and the rest is deposited to heat the YAG crystals. So we employed a laser-diode (LD) which emits light only at wavelengths absorbable by Nd3+ and a slab Nd:YAG crystal in which light travels a zigzag path so as not to cause heat-distortion. We further attempted to amplify high-quality (TEM00), low-intensity light from the Nd:YAG laser in steps through a preamplifier and postamplifiers, thus minimizing effects of heat deposition. All the devices for this system are of all-solid-state (Fig. 4-7). Furthermore, the image transferring technique that transfers the beam image to the next crystal is used to avoid lens effects appearing in laser-heated large crystals. Thus, we have obtained a laser system producing an average pulse energy of 1.25 J at 1,064 nm wavelength and 200 Hz repetition rate. The pulse frequency is converted by a non-linear LBO (LiB3O5) crystal, to produce green light with 105 W average power at 170 Hz for Ti:sapphire pumping. The electricity-to-green light energy conversion efficiency in the system is 2%, far beyond 0.2% in conventional Xe-flash lamps.

Reference K. Tei et al., Diffusion-Bonded KTiOPO4 Crystal for the Second Harmonic Generation of High Average Power Zigzag Slab Nd:YAG Laser, Jpn. J. Appl. Phys., Part 2 Lett., 38(2), 35 (1999).

Select a topic in left column