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A 19 W, TEM(sub 00) mode, Ho:YLF laser pumped by continuous wave Tm:fiber laser has been demonstrated at the room temperature. The slope efficiency and optical-to-optical efficiency are 65% and 55%, respectively.
A conductively-cooled Ho:Tm:LuLiF laser head can amplify 80mJ/340ns probe pulses into 400mJ when the pump pulse energy is close to amplified spontaneous emission (ASE) threshold, 5.6J. For a small signal, the double-pass amplification exceeds 25.
High repetition rate operation of an injection seeded Ho:YLF laser has been demonstrated. For 1 kHz operation, the output pulse energy reaches 5.8mJ and the optical-to-optical efficiency is 39% when the pump power is 14.5W.
An efficient 19 W, TEM(sub 00) mode, Ho:YLF laser pumped by continuous wave Tm:fiber laser has been demonstrated at the room temperature. The slope efficiency and optical-to-optical efficiency are 65% and 55%, respectively.
A single transverse/longitudinal mode, compact Q-switched Ho:YLF laser has been designed and demonstrated for space-borne lidar applications. The pulse energy is between 34-40 mJ for 100-200 Hz operation. The corresponding peak power is >1 MW.
NASA Langley Research Center has a long history of developing 2 micron lasers. From fundamental spectroscopy research, theoretical prediction of new materials, laser demonstration and engineering of lidar systems, it has been a very successful program spanning around two decades. This article covers the program development from the early research to the present instrumentation. A brief historical perspective of Tm:Ho work by early researchers is also given.
Supported by NASA’s Earth Science Technology Office (ESTO), a new lidar transmitter system is developed under the Wind-Space Pathfinder coherent wind lidar project. It is an efficient Ho:LuLiF master oscillator power amplifier system (MOPA) that is capable of generating 15 watts power and 180 ns pulse width at 200 Hz PRF with excellent beam quality. The laser is injection seeded to provide stable single longitudinal frequency output. The laser beam polarization can be switched between “S” and “P” alternatively. Thus, the “S” and “P” beams can be directed to two separate telescopes at different directions to provide true horizontal wind measurement without a moving part in the lidar system. The laser power, pulse width and beam quality fulfill the space lidar system’s figure-of-merit (FOM) and measurement accuracy requirements.
Supported by NASA’s Earth Science Technology Office (ESTO), a new lidar transmitter system is developed under the Wind-Space Pathfinder coherent wind lidar project. It is an efficient Ho:LuLiF master oscillator power amplifier system (MOPA) that is capable of generating 15 watts power and 180 ns pulse width at 200 Hz PRF with excellent beam quality. The laser is injection seeded to provide stable single longitudinal frequency output. The laser beam polarization can be switched between “S” and “P” alternatively. Thus, the “S” and “P” beams can be directed to two separate telescopes at different directions to provide true horizontal wind measurement without a moving part in the lidar system. The laser power, pulse width and beam quality fulfill the space lidar system’s figure-of-merit (FOM) and measurement accuracy requirements.
Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations
LiB(OH)4 crystallizes in the orthorhombic Pbca space group. The structure is three-dimensional. Li1+ is bonded to four O2- atoms to form LiO4 tetrahedra that share corners with four equivalent BO4 tetrahedra. There are a spread of Li–O bond distances ranging from 1.96–2.05 Å. B3+ is bonded to four O2- atoms to form BO4 tetrahedra that share corners with four equivalent LiO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.47–1.51 Å. There are four inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the third H1+ site, H1+ is bonded in a single-bond geometry to two O2- atoms. There is one shorter (1.00 Å) and one longer (1.73 Å) H–O bond length. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to two O2- atoms. There is one shorter (1.00 Å) and one longer (1.67 Å) H–O bond length. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to one Li1+, one B3+, and one H1+ atom. In the second O2- site, O2- is bonded in a 1-coordinate geometry to one Li1+, one B3+, and two H1+ atoms. In the third O2- site, O2- is bonded in a 1-coordinate geometry to one Li1+, one B3+, and two H1+ atoms. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to one Li1+, one B3+, and one H1+ atom.
H3BO3 crystallizes in the triclinic P-1 space group. The structure is two-dimensional and consists of two H3BO3 sheets oriented in the (1, 0, 0) direction. there are two inequivalent B3+ sites. In the first B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. All B–O bond lengths are 1.38 Å. In the second B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. All B–O bond lengths are 1.38 Å. There are six inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a distorted linear geometry to two O2- atoms. There is one shorter (1.00 Å) and one longer (1.65 Å) H–O bond length. In the second H1+ site, H1+ is bonded in a distorted linear geometry to two O2- atoms. There is one shorter (1.00 Å) and one longer (1.65 Å) H–O bond length. In the third H1+ site, H1+ is bonded in a distorted linear geometry to two O2- atoms. There is one shorter (1.00 Å) and one longer (1.65 Å) H–O bond length. In the fourth H1+ site, H1+ is bonded in a distorted linear geometry to two O2- atoms. There is one shorter (1.00 Å) and one longer (1.65 Å) H–O bond length. In the fifth H1+ site, H1+ is bonded in a distorted single-bond geometry to two O2- atoms. There is one shorter (1.00 Å) and one longer (1.65 Å) H–O bond length. In the sixth H1+ site, H1+ is bonded in a distorted linear geometry to two O2- atoms. There is one shorter (1.00 Å) and one longer (1.65 Å) H–O bond length. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to one B3+ and two H1+ atoms. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to one B3+ and two H1+ atoms. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to one B3+ and two H1+ atoms. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to one B3+ and two H1+ atoms. In the fifth O2- site, O2- is bonded in a distorted trigonal planar geometry to one B3+ and two H1+ atoms. In the sixth O2- site, O2- is bonded in a distorted trigonal planar geometry to one B3+ and two H1+ atoms.
Ca(OH)2 crystallizes in the trigonal P-3m1 space group. The structure is two-dimensional and consists of one Ca(OH)2 sheet oriented in the (0, 0, 1) direction. Ca2+ is bonded to six equivalent O2- atoms to form edge-sharing CaO6 octahedra. All Ca–O bond lengths are 2.39 Å. H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.97 Å. O2- is bonded in a distorted single-bond geometry to three equivalent Ca2+ and one H1+ atom.
Ca3Al2(OH)12 crystallizes in the cubic Ia-3d space group. The structure is three-dimensional. Ca2+ is bonded in a distorted body-centered cubic geometry to eight equivalent O2- atoms. There are four shorter (2.47 Å) and four longer (2.55 Å) Ca–O bond lengths. Al3+ is bonded in an octahedral geometry to six equivalent O2- atoms. All Al–O bond lengths are 1.93 Å. H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.97 Å. O2- is bonded in a distorted single-bond geometry to two equivalent Ca2+, one Al3+, and one H1+ atom.
KLi2HO3H2 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional and consists of two dihydrogen molecules and one KLi2HO3 framework. In the KLi2HO3 framework, K1+ is bonded in a 4-coordinate geometry to four O2- atoms. There are a spread of K–O bond distances ranging from 2.55–3.05 Å. Li1+ is bonded in a 4-coordinate geometry to four O2- atoms. There are a spread of Li–O bond distances ranging from 1.88–2.03 Å. H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.97 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to one K1+, two equivalent Li1+, and one O2- atom. The O–O bond length is 1.53 Å. In the second O2- site, O2- is bonded in a 6-coordinate geometry to three equivalent K1+, two equivalent Li1+, and one O2- atom. In the third O2- site, O2- is bonded in a distorted single-bond geometry to four equivalent Li1+ and one H1+ atom.
Gd(OH)3 crystallizes in the hexagonal P6_3/m space group. The structure is three-dimensional. Gd3+ is bonded in a 9-coordinate geometry to nine equivalent O2- atoms. There are six shorter (2.47 Å) and three longer (2.49 Å) Gd–O bond lengths. H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.97 Å. O2- is bonded in a single-bond geometry to three equivalent Gd3+ and one H1+ atom.
Dy(OH)3 crystallizes in the hexagonal P6_3/m space group. The structure is three-dimensional. Dy3+ is bonded in a 9-coordinate geometry to nine equivalent O2- atoms. There are six shorter (2.42 Å) and three longer (2.48 Å) Dy–O bond lengths. H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.97 Å. O2- is bonded in a single-bond geometry to three equivalent Dy3+ and one H1+ atom.
Y(OH)3 crystallizes in the hexagonal P6_3/m space group. The structure is three-dimensional. Y3+ is bonded in a 9-coordinate geometry to nine equivalent O2- atoms. There are six shorter (2.43 Å) and three longer (2.49 Å) Y–O bond lengths. H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.97 Å. O2- is bonded in a single-bond geometry to three equivalent Y3+ and one H1+ atom.
Tb(OH)3 crystallizes in the hexagonal P6_3/m space group. The structure is three-dimensional. Tb3+ is bonded in a 9-coordinate geometry to nine equivalent O2- atoms. There are six shorter (2.44 Å) and three longer (2.47 Å) Tb–O bond lengths. H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.97 Å. O2- is bonded in a single-bond geometry to three equivalent Tb3+ and one H1+ atom.