Development of high coherence, 200mW, 193nm solid-state laser at 6 kHz

Abstract

The high coherent, high power 193-nm ArF lasers are useful for interference lithography and microprosessing applications. In order to achieve high coherence ArF lasers, we have been developing a high coherence 193 nm solid state laser for the seeding to a high power ArF laser. We used the sum frequency mixing of the fourth harmonic (FH) of a 904-nm Ti:sapphire laser with a Nd:YVO 4 laser (1342 nm) to generate 193-nm light. The laser system consists of a single-mode Ti:sapphire oscillator seeded by a 904-nm external cavity laser diode, a Pockels cell, a 6-pass amplifier, a 4-pass amplifier, a 2-pass amplifier and a wavelength conversion stage. The required repetition rate of 6 kHz corresponding to the ArF laser, along with a low gain at 904 nm induces serious thermal lens effects; extremely short focal lengths of the order of cm and bi-foci in the vertical and horizontal directions. From the analysis of thermal lens depending on pump intensity, we successfully compensated the thermal lens by dividing a 527-nm pump power with 15, 25 and 28 W to 3-stage amplifiers with even passes, resulting in the output power above 10W with a nearly diffraction limited beam. This 904-nm output was converted to 3.8 W in the second harmonic by LBO, 0.5 W in FH by BBO sequentially. Finally the output power of 230 mW was obtained at 193 nm by mixing the FH with a 1342-nm light in CLBO.

High-Power, Solid-State, Deep Ultraviolet Laser Generation

“…For the CLBO crystal, J. Sakuma reported a 120 mW DUV laser output at 193.4 nm by SFG between 234.1 nm and 1110 nm, which is the highest solid-state CW 193-nm laser until now [18]. Other results of 193 nm generation by SFG in CLBO also could reach to the average power from 100 mW to 300 mW [12,31,32]. CLBO has a larger d eff than LBO and a smaller walk-off angle than BBO, which means it could lead to a higher power DUV laser with better beam quality at the same time.…”

High Energy, High Peak Power 1342-nm Picosecond Nd:YVO4Regenerative Amplifier

“…For example, high power blue light (440 nm) can be generated by frequency tripling of 1.3 μm laser, which is desired for optical data storage, large image projection and medical applications [3]. Especially, the sum frequency mixing of a 1342 nm Nd:YVO 4 laser with the fourth harmonic of a 904 nm Ti:sapphire laser is used to generate 193 nm light for the seeding to a high power ArF laser [4], or an all solid-state deep-UV light source at 191.7 nm can be obtained by seventh harmonic generation from 1342 nm [5], which is useful for interference lithography and microprosessing applications. Moreover, laser sources from 160∼170 nm in the deep-ultraviolet (DUV) region obtained by eighth harmonic generation of 1.3 μm lasers have higher photon energy than traditional 177.3 nm, which may be used in photoemission spectroscopy for measuring the superconducting energy gaps of f -electron superconductors [6].…”

High average power picosecond and nanosecond laser operating at 1342nm wavelength

“…Caused by emerging applications, remarkable progress have been made over the past decade in power and energy scaling of CW, Q-switched and mode-locked lasers running at 1342 nm wavelength [1][2][3][4][5][6][7][8][9] . Side-pumped bounce geometry 1 Nd:YVO 4 CW MOPA produces 19.6 W. Higher ~ 26 W output power with M 2 > 30 achieved 2 Short pulsewidth Nd:YVO 4 lasers with output power above 1 W at 1342 nm have been reported in ref.…”