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## Sub-joule Picosecond Nd:YAG Lasers for Precision Lunar Laser Ranging

Transactions of IAA RAS, issue 58, 41–50 (2021)

Keywords: Nd:YAG laser, solid state laser, microchip laser, regenerative amplifier, Lunar Laser Ranging

### Abstract

Here we report on the comparison of two schemes of high-power picosecond laser amplifiers with a sub-Joule output energy, operating at a pulse repetition rate of 200 Hz, which can be used in Lunar Laser Ranging (LLR). First scheme (1) is a single-stage six-pass scheme based on a single Nd:YAG Ø15 × 140 mm laser rod. Second scheme (2) is a two-stage two-pass scheme based on two Nd:YAG laser rods with Ø15 × 140 mm and Ø10 × 140 mm dimensions. The paper presents the main experimental results of testing each scheme and their comparison. The output energy of 1064 nm radiation pulses in schemes (1) and (2) was 0.53 J and 0.92 J, the pulse duration was 81 ps and 71 ps, respectively. The output radiation in each scheme was converted to the second harmonic using an LBO crystal. The efficiency of second harmonic generation in schemes (1) and (2) was 54 % and 79 %, respectively. The pulse energy at a wavelength of 532 nm was 286 mJ and 730 mJ in schemes (1) and (2), respectively. The output energy of scheme (2) was limited by the effect of small-scale self-focusing. Both developed schemes have high pulse shape stability, high output energy and high pulse repetition rate. The single-stage scheme (1) has a lower cost due to the use of one amplification stage, but it is more complex. The pulse energy at the output of the amplifier (1) is sufficient for LLR. Compared to scheme (1), scheme (2) is resistant to misalignments; it is easier to compensate the thermally-induced birefringence and nonstationary wavefront distortions in laser rods. Scheme (2) allows to obtain a flat-top intensity distribution in the near field and a lower divergence of the output radiation. To the best of our knowledge, the output energy level at wavelengths of 1064 nm and 532 nm, which were obtained in scheme (2), are a record for this class of lasers.

### Citation

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A. F. Kornev, R. V. Balmashnov, V. V. Koval. Sub-joule Picosecond Nd:YAG Lasers for Precision Lunar Laser Ranging // Transactions of IAA RAS. — 2021. — Issue 58. — P. 41–50. @article{kornev2021, abstract = {Here we report on the comparison of two schemes of high-power picosecond laser amplifiers with a sub-Joule output energy, operating at a pulse repetition rate of 200 Hz, which can be used in Lunar Laser Ranging (LLR). First scheme (1) is a single-stage six-pass scheme based on a single Nd:YAG Ø15 × 140 mm laser rod. Second scheme (2) is a two-stage two-pass scheme based on two Nd:YAG laser rods with Ø15 × 140 mm and Ø10 × 140 mm dimensions. The paper presents the main experimental results of testing each scheme and their comparison. The output energy of 1064 nm radiation pulses in schemes (1) and (2) was 0.53 J and 0.92 J, the pulse duration was 81 ps and 71 ps, respectively. The output radiation in each scheme was converted to the second harmonic using an LBO crystal. The efficiency of second harmonic generation in schemes (1) and (2) was 54 % and 79 %, respectively. The pulse energy at a wavelength of 532 nm was 286 mJ and 730 mJ in schemes (1) and (2), respectively. The output energy of scheme (2) was limited by the effect of small-scale self-focusing. Both developed schemes have high pulse shape stability, high output energy and high pulse repetition rate. The single-stage scheme (1) has a lower cost due to the use of one amplification stage, but it is more complex. The pulse energy at the output of the amplifier (1) is sufficient for LLR. Compared to scheme (1), scheme (2) is resistant to misalignments; it is easier to compensate the thermally-induced birefringence and nonstationary wavefront distortions in laser rods. Scheme (2) allows to obtain a flat-top intensity distribution in the near field and a lower divergence of the output radiation. To the best of our knowledge, the output energy level at wavelengths of 1064 nm and 532 nm, which were obtained in scheme (2), are a record for this class of lasers.}, author = {A.~F. Kornev and R.~V. Balmashnov and V.~V. Koval}, doi = {10.32876/ApplAstron.58.41-50}, issue = {58}, journal = {Transactions of IAA RAS}, keyword = {Nd:YAG laser, solid state laser, microchip laser, regenerative amplifier, Lunar Laser Ranging}, pages = {41--50}, title = {Sub-joule Picosecond Nd:YAG Lasers for Precision Lunar Laser Ranging}, url = {http://iaaras.ru/en/library/paper/2097/}, year = {2021} } TY - JOUR TI - Sub-joule Picosecond Nd:YAG Lasers for Precision Lunar Laser Ranging AU - Kornev, A. F. AU - Balmashnov, R. V. AU - Koval, V. V. PY - 2021 T2 - Transactions of IAA RAS IS - 58 SP - 41 AB - Here we report on the comparison of two schemes of high-power picosecond laser amplifiers with a sub-Joule output energy, operating at a pulse repetition rate of 200 Hz, which can be used in Lunar Laser Ranging (LLR). First scheme (1) is a single-stage six-pass scheme based on a single Nd:YAG Ø15 × 140 mm laser rod. Second scheme (2) is a two-stage two-pass scheme based on two Nd:YAG laser rods with Ø15 × 140 mm and Ø10 × 140 mm dimensions. The paper presents the main experimental results of testing each scheme and their comparison. The output energy of 1064 nm radiation pulses in schemes (1) and (2) was 0.53 J and 0.92 J, the pulse duration was 81 ps and 71 ps, respectively. The output radiation in each scheme was converted to the second harmonic using an LBO crystal. The efficiency of second harmonic generation in schemes (1) and (2) was 54 % and 79 %, respectively. The pulse energy at a wavelength of 532 nm was 286 mJ and 730 mJ in schemes (1) and (2), respectively. The output energy of scheme (2) was limited by the effect of small-scale self-focusing. Both developed schemes have high pulse shape stability, high output energy and high pulse repetition rate. The single-stage scheme (1) has a lower cost due to the use of one amplification stage, but it is more complex. The pulse energy at the output of the amplifier (1) is sufficient for LLR. Compared to scheme (1), scheme (2) is resistant to misalignments; it is easier to compensate the thermally-induced birefringence and nonstationary wavefront distortions in laser rods. Scheme (2) allows to obtain a flat-top intensity distribution in the near field and a lower divergence of the output radiation. To the best of our knowledge, the output energy level at wavelengths of 1064 nm and 532 nm, which were obtained in scheme (2), are a record for this class of lasers. DO - 10.32876/ApplAstron.58.41-50 UR - http://iaaras.ru/en/library/paper/2097/ ER -