The Experts below are selected from a list of 111291 Experts worldwide ranked by ideXlab platform
Kodo Kawase - One of the best experts on this subject based on the ideXlab platform.
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Kilowatt-peak Terahertz-Wave Generation and Sub-femtojoule Terahertz-Wave Pulse Detection Based on Nonlinear Optical Wavelength-conversion at Room Temperature
Journal of Infrared Millimeter and Terahertz Waves, 2014Co-Authors: Hiroaki Minamide, Junichi Shikata, Shin’ichiro Hayashi, Koji Nawata, Takunori Taira, Kodo KawaseAbstract:Intense Terahertz (THz)-Wave Generation and highly sensitive THz-Wave detection were obtained by Wavelength conversion with nonlinear optical susceptibility χ^(2) of LiNbO_3 crystals. Maximum peak output of about 50 kW (5 μJ/pulse) was demonstrated in an injection-seeded THz-Wave parametric generator pumped by post-amplified emission from a microchip Nd:YAG laser. Using the sub-nanosecond pulse duration of the laser proposed herein provides effective mitigation of stimulated Brillouin scattering in LiNbO_3, producing higher gain for Wavelength conversion between near-infrared (near-IR) pump light and THz Waves. Monochromatic THz radiation was obtained in the continuous tuning range of 0.7–2.9 THz. Additionally, highly sensitive THz-Wave detection was demonstrated based on up-conversion from THz Waves to near-IR light as well as efficient THz-Wave Generation. The signal generated with non-collinear phase-matching condition showed spectroscopic detection on the screen apart from the LiNbO_3 crystal. Highly sensitive detection with minimum energy of about 80 aJ/pulse (0.8 μW at peak) and a large dynamic range of more than 100 dB were achieved in this experiment.
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Broadband THz-Wave Generation by satisfying the noncollinear phase-matching condition with a reflected signal beam.
Applied optics, 2013Co-Authors: Takuya Akiba, Katsuhiko Miyamoto, Yasuhiro Akimoto, Motoaki Tamura, Koji Suizu, Takashige Omatsu, Jun Takayanagi, Tomoya Takada, Kodo KawaseAbstract:We demonstrated broadband terahertz (THz) Wave Generation by satisfying the noncollinear phase-matching condition with a reflected signal beam. We constructed a dual-Wavelength optical parametric oscillator with two potassium titanium oxide phosphate crystals pumped by a frequency-doubled Nd:YAG laser. The collinear pump and signal Waves were irradiated into a lithium niobate crystal. The pump and the signal Waves were reflected at the crystal surface. Because the pump and the signal Waves have a finite beam diameter, when the reflected signal Wave and unreflected pump Wave were irradiated at the correct angle, the noncollinear phase-matching condition was satisfied. By changing the incident angle to the crystal, broadband THz-Wave Generation with a range of over 0.2-7.2 THz was achieved.
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wide spectrum terahertz Wave Generation from nonlinear Waveguides
IEEE Journal of Selected Topics in Quantum Electronics, 2013Co-Authors: Kei Takeya, Koji Suizu, H Sai, Toshihiko Ouchi, Kodo KawaseAbstract:We have obtained efficient terahertz (THz)-Wave Generation from surface-emitting or Waveguide propagation using Cherenkov-type radiation with nonlinear optical (NLO) crystals. This approach presented the following advantages: 1) many crystals can be used as THz-Wave emitters; 2) it is not necessary to satisfy the phase-matching condition inside the crystal; and 3) THz-Wave Generation is not suppressed by the absorption in the crystal. We demonstrated that the THz-Wave Generation was enhanced 50× by suppressing the phase mismatch with a surfing configuration for bulk lithium niobate (LiNbO3) crystals. Using the prism-coupled Cherenkov phase-matching method with organic crystal 4-dimethylamino-N-metyl-4-stilbazolium tosylate, we produced tunable THz radiation within ~0.1-10 THz. There was no evidence of significant absorption in the crystal. To show the advantages of the Waveguide emitter, we demonstrated THz Generation using a ridge-type LiNbO3 Waveguide with a thickness of 3.8 μm. We obtained THz-Wave Generation with an ideal temporal half-cycle pulse and a wide tuning range, which is applied to reflection tomography imaging.
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cherenkov phase matched monochromatic tunable terahertz Wave Generation
2010Co-Authors: Koji Suizu, Takayuki Shibuya, Kodo KawaseAbstract:Terahertz (THz) Waves present attractive possibilities in advanced applications including biomedical analysis and stand-off detection for hazardous materials. The development of monochromatic and tunable coherent THz-Wave sources is of great interest for use in these applications. Recently, a parametric process based on second-order nonlinearities was used to generate tunable monochromatic coherent THz Waves using nonlinear optical crystals (Boyd et al., 1972; Rice et al., 1994; Shi et al., 2002; Tanabe et al. 2003). In general, however, nonlinear optical materials have high absorption coefficients in the THz-Wave region, which inhibits efficient THz-Wave Generation. Avetisyan et al. proposed surface-emitting THz-Wave Generation using the difference frequency Generation (DFG) technique in a periodically poled lithium niobate (PPLN) Waveguide to overcome these problems (Avetisyan et al., 2002). A surface-emitted THz Wave radiates from the surface of the PPLN and propagates perpendicular to the direction of the pump beam. The absorption loss is minimized because the THz Wave is generated from the PPLN surface. Moreover, the phase-matching condition can be designed using PPLN with an appropriate grating period (Sasaki et al., 2002). Surface-emitted THz-Wave devices have the potential for high conversion efficiency, and continuous Wave THz-Wave Generation has been successfully demonstrated (Sasaki et al., 2005). Unfortunately, the tuning range of the THz Waves is limited to about 100 GHz by the nature of PPLN, and a wide tuning range cannot be realized using the quasi-phase–matching method. We developed a Cherenkov phase-matching method for monochromatic THz-Wave Generation using the DFG process with a lithium niobate crystal, which resulted in both high conversion efficiency and wide tunability. Although THz-Wave Generation by Cherenkov phase matching has been demonstrated using femtosecond pumping pulses (Auston et al., 1984; Kleinman et al., 1984; Hebling et al., 2002; Wahlstrand, 2003; Badrov et al., 2009), producing very high peak power (Yeh et al., 2007), these THz-Wave sources are not monochromatic. Our method generates monochromatic and tunable THz Waves using a nanosecond pulsed laser source.
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extremely frequency widened terahertz Wave Generation using cherenkov type radiation
Optics Express, 2009Co-Authors: Koji Suizu, Takuya Akiba, Takayuki Shibuya, Kaoru Koketsu, Toshihiro Tsutsui, Kodo KawaseAbstract:Terahertz (THz) Wave Generation based on nonlinear frequency conversion is promising way for realizing a tunable monochromatic bright THz-Wave source. Such a development of efficient and wide tunable THz-Wave source depends on discovery of novel brilliant nonlinear crystal. Important factors of a nonlinear crystal for THz-Wave Generation are, 1. High nonlinearity and 2. Good transparency at THz frequency region. Unfortunately, many nonlinear crystals have strong absorption at THz frequency region. The fact limits efficient and wide tunable THz-Wave Generation. Here, we show that Cherenkov radiation with Waveguide structure is an effective strategy for achieving efficient and extremely wide tunable THz-Wave source. We fabricated MgO-doped lithium niobate slab Waveguide with 3.8 μm of thickness and demonstrated difference frequency Generation of THz-Wave Generation with Cherenkov phase matching. Extremely frequency-widened THz-Wave Generation, from 0.1 to 7.2 THz, without no structural dips successfully obtained. The tuning frequency range of Waveguided Cherenkov radiation source was extremely widened compare to that of injection seeded-Terahertz Parametric Generator. The tuning range obtained in this work for THz-Wave Generation using lithium niobate crystal was the widest value in our knowledge. The highest THz-Wave energy obtained was about 3.2 pJ, and the energy conversion efficiency was about 10-5 %. The method can be easily applied for many conventional nonlinear crystals, results in realizing simple, reasonable, compact, high efficient and ultra broad band THz-Wave sources.
Koji Suizu - One of the best experts on this subject based on the ideXlab platform.
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behavior of three Waves in cherenkov phase matched monochromatic terahertz Wave Generation investigated by numerical analysis
Japanese Journal of Applied Physics, 2014Co-Authors: Koji Suizu, Takuya AkibaAbstract:The dynamical behavior of electric fields in Cherenkov phase matched terahertz Wave Generation was numerically analyzed. The effect of diffraction of the terahertz Wave was the dominant factor for efficiency of terahertz Wave Generation. Tightly-focused pump and signal beams radiated efficient terahertz Wave drastically in the transverse direction. Propagating terahertz Wave at the Cherenkov angle separated from the pump and signal beams; thus destructive interaction of the three Waves under phase mismatched conditions no longer occurred. The effect resulted in continuous pump depletion and efficient energy conversion from the pump Wave to the terahertz Wave. Our results indicate that complete pump depletion could be achieved with Cherenkov phase matching.
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Broadband THz-Wave Generation by satisfying the noncollinear phase-matching condition with a reflected signal beam.
Applied optics, 2013Co-Authors: Takuya Akiba, Katsuhiko Miyamoto, Yasuhiro Akimoto, Motoaki Tamura, Koji Suizu, Takashige Omatsu, Jun Takayanagi, Tomoya Takada, Kodo KawaseAbstract:We demonstrated broadband terahertz (THz) Wave Generation by satisfying the noncollinear phase-matching condition with a reflected signal beam. We constructed a dual-Wavelength optical parametric oscillator with two potassium titanium oxide phosphate crystals pumped by a frequency-doubled Nd:YAG laser. The collinear pump and signal Waves were irradiated into a lithium niobate crystal. The pump and the signal Waves were reflected at the crystal surface. Because the pump and the signal Waves have a finite beam diameter, when the reflected signal Wave and unreflected pump Wave were irradiated at the correct angle, the noncollinear phase-matching condition was satisfied. By changing the incident angle to the crystal, broadband THz-Wave Generation with a range of over 0.2-7.2 THz was achieved.
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wide spectrum terahertz Wave Generation from nonlinear Waveguides
IEEE Journal of Selected Topics in Quantum Electronics, 2013Co-Authors: Kei Takeya, Koji Suizu, H Sai, Toshihiko Ouchi, Kodo KawaseAbstract:We have obtained efficient terahertz (THz)-Wave Generation from surface-emitting or Waveguide propagation using Cherenkov-type radiation with nonlinear optical (NLO) crystals. This approach presented the following advantages: 1) many crystals can be used as THz-Wave emitters; 2) it is not necessary to satisfy the phase-matching condition inside the crystal; and 3) THz-Wave Generation is not suppressed by the absorption in the crystal. We demonstrated that the THz-Wave Generation was enhanced 50× by suppressing the phase mismatch with a surfing configuration for bulk lithium niobate (LiNbO3) crystals. Using the prism-coupled Cherenkov phase-matching method with organic crystal 4-dimethylamino-N-metyl-4-stilbazolium tosylate, we produced tunable THz radiation within ~0.1-10 THz. There was no evidence of significant absorption in the crystal. To show the advantages of the Waveguide emitter, we demonstrated THz Generation using a ridge-type LiNbO3 Waveguide with a thickness of 3.8 μm. We obtained THz-Wave Generation with an ideal temporal half-cycle pulse and a wide tuning range, which is applied to reflection tomography imaging.
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cherenkov phase matched monochromatic tunable terahertz Wave Generation
2010Co-Authors: Koji Suizu, Takayuki Shibuya, Kodo KawaseAbstract:Terahertz (THz) Waves present attractive possibilities in advanced applications including biomedical analysis and stand-off detection for hazardous materials. The development of monochromatic and tunable coherent THz-Wave sources is of great interest for use in these applications. Recently, a parametric process based on second-order nonlinearities was used to generate tunable monochromatic coherent THz Waves using nonlinear optical crystals (Boyd et al., 1972; Rice et al., 1994; Shi et al., 2002; Tanabe et al. 2003). In general, however, nonlinear optical materials have high absorption coefficients in the THz-Wave region, which inhibits efficient THz-Wave Generation. Avetisyan et al. proposed surface-emitting THz-Wave Generation using the difference frequency Generation (DFG) technique in a periodically poled lithium niobate (PPLN) Waveguide to overcome these problems (Avetisyan et al., 2002). A surface-emitted THz Wave radiates from the surface of the PPLN and propagates perpendicular to the direction of the pump beam. The absorption loss is minimized because the THz Wave is generated from the PPLN surface. Moreover, the phase-matching condition can be designed using PPLN with an appropriate grating period (Sasaki et al., 2002). Surface-emitted THz-Wave devices have the potential for high conversion efficiency, and continuous Wave THz-Wave Generation has been successfully demonstrated (Sasaki et al., 2005). Unfortunately, the tuning range of the THz Waves is limited to about 100 GHz by the nature of PPLN, and a wide tuning range cannot be realized using the quasi-phase–matching method. We developed a Cherenkov phase-matching method for monochromatic THz-Wave Generation using the DFG process with a lithium niobate crystal, which resulted in both high conversion efficiency and wide tunability. Although THz-Wave Generation by Cherenkov phase matching has been demonstrated using femtosecond pumping pulses (Auston et al., 1984; Kleinman et al., 1984; Hebling et al., 2002; Wahlstrand, 2003; Badrov et al., 2009), producing very high peak power (Yeh et al., 2007), these THz-Wave sources are not monochromatic. Our method generates monochromatic and tunable THz Waves using a nanosecond pulsed laser source.
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extremely frequency widened terahertz Wave Generation using cherenkov type radiation
Optics Express, 2009Co-Authors: Koji Suizu, Takuya Akiba, Takayuki Shibuya, Kaoru Koketsu, Toshihiro Tsutsui, Kodo KawaseAbstract:Terahertz (THz) Wave Generation based on nonlinear frequency conversion is promising way for realizing a tunable monochromatic bright THz-Wave source. Such a development of efficient and wide tunable THz-Wave source depends on discovery of novel brilliant nonlinear crystal. Important factors of a nonlinear crystal for THz-Wave Generation are, 1. High nonlinearity and 2. Good transparency at THz frequency region. Unfortunately, many nonlinear crystals have strong absorption at THz frequency region. The fact limits efficient and wide tunable THz-Wave Generation. Here, we show that Cherenkov radiation with Waveguide structure is an effective strategy for achieving efficient and extremely wide tunable THz-Wave source. We fabricated MgO-doped lithium niobate slab Waveguide with 3.8 μm of thickness and demonstrated difference frequency Generation of THz-Wave Generation with Cherenkov phase matching. Extremely frequency-widened THz-Wave Generation, from 0.1 to 7.2 THz, without no structural dips successfully obtained. The tuning frequency range of Waveguided Cherenkov radiation source was extremely widened compare to that of injection seeded-Terahertz Parametric Generator. The tuning range obtained in this work for THz-Wave Generation using lithium niobate crystal was the widest value in our knowledge. The highest THz-Wave energy obtained was about 3.2 pJ, and the energy conversion efficiency was about 10-5 %. The method can be easily applied for many conventional nonlinear crystals, results in realizing simple, reasonable, compact, high efficient and ultra broad band THz-Wave sources.
Hiroaki Minamide - One of the best experts on this subject based on the ideXlab platform.
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terahertz Wave Generation from 4 dimethylamino n methyl 4 stilbazolium p bromobenzenesulfonate crystal effect of halogen substitution in a counter benzenesulfonate of stilbazolium derivatives
Optical Materials, 2014Co-Authors: Takeshi Matsukawa, T Notake, Kouji Nawata, Shunsuke Inada, Shuji Okada, Hiroaki MinamideAbstract:Abstract We have developed a technique to grow 4-dimethylamino- N ′-methyl-4′-stilbazolium p -bromobenzenesulfonate (DASB) with a halogen (bromine) substituent in the anion for THz-Wave Generation. The bulky DASB single crystals, typically measuring 3 × 3 × 0.2 mm 3 , are grown from a methanol solution by the slow-cooling method over a 5-week period. Compared with 4-dimethylamino- N ′-methyl-4′-stilbazolium tosylate (DAST), the DASB crystal showed high transmittance at around 3 THz and in the region above 100 THz. Using the difference frequency Generation process, we can obtain a broadband THz-Wave between 2 and 25 THz from a DASB crystal. Moreover, the output THz-Wave power between 2.5 and 5.5 THz generated from DASB is high, confirming that halogen substitution in the anion of stilbazolium derivatives enables efficient THz-Wave Generation in the region between 2.5 and 5.5 THz.
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Kilowatt-peak Terahertz-Wave Generation and Sub-femtojoule Terahertz-Wave Pulse Detection Based on Nonlinear Optical Wavelength-conversion at Room Temperature
Journal of Infrared Millimeter and Terahertz Waves, 2014Co-Authors: Hiroaki Minamide, Junichi Shikata, Shin’ichiro Hayashi, Koji Nawata, Takunori Taira, Kodo KawaseAbstract:Intense Terahertz (THz)-Wave Generation and highly sensitive THz-Wave detection were obtained by Wavelength conversion with nonlinear optical susceptibility χ^(2) of LiNbO_3 crystals. Maximum peak output of about 50 kW (5 μJ/pulse) was demonstrated in an injection-seeded THz-Wave parametric generator pumped by post-amplified emission from a microchip Nd:YAG laser. Using the sub-nanosecond pulse duration of the laser proposed herein provides effective mitigation of stimulated Brillouin scattering in LiNbO_3, producing higher gain for Wavelength conversion between near-infrared (near-IR) pump light and THz Waves. Monochromatic THz radiation was obtained in the continuous tuning range of 0.7–2.9 THz. Additionally, highly sensitive THz-Wave detection was demonstrated based on up-conversion from THz Waves to near-IR light as well as efficient THz-Wave Generation. The signal generated with non-collinear phase-matching condition showed spectroscopic detection on the screen apart from the LiNbO_3 crystal. Highly sensitive detection with minimum energy of about 80 aJ/pulse (0.8 μW at peak) and a large dynamic range of more than 100 dB were achieved in this experiment.
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intracavity widely tunable monochromatic terahertz Wave Generation with organic bna crystal and ktp opo
Conference on Lasers and Electro-Optics, 2011Co-Authors: Ming Tang, Kouji Nawata, T Notake, Yuye Wang, Hiroaki MinamideAbstract:We demonstrated an efficient intracavity terahertz-Wave Generation with organic BNA crystal inside a dual-Wavelength KTP-OPO cavity. Widely tunable monochromatic terahertz-Wave covering 0.9∼20 THz has been generated with enhanced pump intensity.
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monochromatic wide tunable terahertz Wave Generation and detection system working at room temperature
International Conference on Infrared Millimeter and Terahertz Waves, 2009Co-Authors: J Z Zhang, Hiroaki MinamideAbstract:An automatic phase matching technology, integrated with an angle-tuning mirror and a telescope, was designed for a surface emitted terahertz-Wave (THz) parametric oscillator and a THz-Wave detection unit using parametric up-conversion in MgO:LiNbO 3 . A monochromatic, wide tunable THz-Wave Generation and detection system working at room temperature was demonstrated. The system offers a dynamic range greater than 25dB and covers a frequency range of 1.2–2.6 THz.
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coherent tunable monochromatic terahertz Wave Generation using n benzyl 2 methyl 4 nitroaniline bna crystal
Proceedings of SPIE, 2008Co-Authors: Katsuhiko Miyamoto, Hiroaki Minamide, Masazumi Fujiwara, Hideki HashimotoAbstract:Widely tunable terahertz (THz) -Wave Generation using difference frequency Generation (DFG) in an organic N-Benzyl-2-methyl-4-nitroaniline (BNA) crystal was demonstrated. An organic nonlinear optical (NLO) BNA crystal is one of the promising materials for efficient and strong THz-Wave Generation because of its potential to have a sufficiently large enough second-order optical nonlinearity. Large and high quality single crystals of BNA (Φ8×30mm) were successfully grown by a vertical Bridgman method. The NLO coefficient d33 of BNA crystal is about 230pm/V. It is the largest value reported for any yellow-colored NLO materials. BNA has low refractive index dispersion between the optical and THz-Wave region, therefore the colinear phase matching condition of the Type0 configuration is satisfied by using 0.7~1μm band pump Wavelength. So, we developed a near-infrared dual-Wavelength pump source for BNA-DFG. Two KTiOPO4 (KTP) crystals were mounted on galvano scanners inside a double-pass optical parametric oscillator (OPO). It is pumped using a frequency-doubled Nd:YAG laser (532 nm, 8 ns, 100 Hz). The signal Wave of the KTP-OPO output was controlled independently and rapidly using a galvano scanner. We successfully generated THz-Wave using organic BNA crystal. The THz-Wave Generation range is from 0.1 to 15THz, while the pumping dual-Wavelength is controlled in the 0.8-0.9μm range.© (2008) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Hiromasa Ito - One of the best experts on this subject based on the ideXlab platform.
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widely tunable terahertz Wave Generation using an n benzyl 2 methyl 4 nitroaniline crystal
Optics Letters, 2008Co-Authors: Katsuhiko Miyamoto, Hiroaki Minamide, Masazumi Fujiwara, Hideki Hashimoto, Hiromasa ItoAbstract:Widely tunable terahertz (THz)-Wave Generation using difference frequency Generation (DFG) in an organic N-benzyl-2-methyl-4-nitroaniline (BNA) crystal was demonstrated. To our knowledge, this is the first report of THz-Wave Generation by BNA DFG. Large, high-quality single crystals of BNA (phi 8 mm x 30 mm) were grown using the vertical Bridgman method. The nonlinear optical (NLO) coefficient d(33) of the BNA crystal is approximately 234 pm/V, which is the largest value reported for any yellow NLO material. The collinear phase-matching condition of the type-0 configuration is satisfied using a 0.7-1 microm band pump Wavelength. We generated THz Waves using an organic BNA crystal; the Generation range is 0.1-15 THz.
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using of 2d ppln crystal for surface emitted thz Wave Generation by optical rectification of laser pulses
15th International Conference on Ultrafast Phenomena (2006) paper MH19, 2006Co-Authors: Yu H Avetisyan, Karo Khachatryan, Hiromasa ItoAbstract:The 2 dimensional periodically poled lithium niobate (2D PPLN) crystal is proposed for narrow-band THz-Wave Generation by optical rectification of ultrashort pulses in surface emitting geometry. The high-energy and wide-aperture optical beam may be used due to opportunity of vector phase-matched interaction in 2D PPLN. The amplitude of electrical field over 10 kV/cm is estimated.
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surface emitted thz Wave Generation amplification using ridge type ppln
Quantum Electronics and Laser Science Conference, 2006Co-Authors: K Suizu, Hiromasa Ito, Yuji Suzuki, Y Sasaki, Yu H AvetisyanAbstract:Surface-emitted THz-Wave Generation using difference frequency mixing with ridge-shaped periodically poled lithium niobate (PPLN) was demonstrated. The PPLN produces THz-Waves in opposite directions, and overlapping each THz-Wave increased the total THz-Wave intensity about 2.7 times.
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coherent tunable thz Wave Generation from linbo3 with monolithic grating coupler
Applied Physics Letters, 1996Co-Authors: Kodo Kawase, Tetsuo Taniuchi, Manabu Sato, Hiromasa ItoAbstract:Coherent THz‐Wave Generation is demonstrated utilizing a grating coupler fabricated on the surface of a LiNbO3 crystal pumped by a Q‐switched Nd:YAG laser. Wide tunability, sharp directivity, and high efficiency were achieved.
Takuya Akiba - One of the best experts on this subject based on the ideXlab platform.
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behavior of three Waves in cherenkov phase matched monochromatic terahertz Wave Generation investigated by numerical analysis
Japanese Journal of Applied Physics, 2014Co-Authors: Koji Suizu, Takuya AkibaAbstract:The dynamical behavior of electric fields in Cherenkov phase matched terahertz Wave Generation was numerically analyzed. The effect of diffraction of the terahertz Wave was the dominant factor for efficiency of terahertz Wave Generation. Tightly-focused pump and signal beams radiated efficient terahertz Wave drastically in the transverse direction. Propagating terahertz Wave at the Cherenkov angle separated from the pump and signal beams; thus destructive interaction of the three Waves under phase mismatched conditions no longer occurred. The effect resulted in continuous pump depletion and efficient energy conversion from the pump Wave to the terahertz Wave. Our results indicate that complete pump depletion could be achieved with Cherenkov phase matching.
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Broadband THz-Wave Generation by satisfying the noncollinear phase-matching condition with a reflected signal beam.
Applied optics, 2013Co-Authors: Takuya Akiba, Katsuhiko Miyamoto, Yasuhiro Akimoto, Motoaki Tamura, Koji Suizu, Takashige Omatsu, Jun Takayanagi, Tomoya Takada, Kodo KawaseAbstract:We demonstrated broadband terahertz (THz) Wave Generation by satisfying the noncollinear phase-matching condition with a reflected signal beam. We constructed a dual-Wavelength optical parametric oscillator with two potassium titanium oxide phosphate crystals pumped by a frequency-doubled Nd:YAG laser. The collinear pump and signal Waves were irradiated into a lithium niobate crystal. The pump and the signal Waves were reflected at the crystal surface. Because the pump and the signal Waves have a finite beam diameter, when the reflected signal Wave and unreflected pump Wave were irradiated at the correct angle, the noncollinear phase-matching condition was satisfied. By changing the incident angle to the crystal, broadband THz-Wave Generation with a range of over 0.2-7.2 THz was achieved.
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extremely frequency widened terahertz Wave Generation using cherenkov type radiation
Optics Express, 2009Co-Authors: Koji Suizu, Takuya Akiba, Takayuki Shibuya, Kaoru Koketsu, Toshihiro Tsutsui, Kodo KawaseAbstract:Terahertz (THz) Wave Generation based on nonlinear frequency conversion is promising way for realizing a tunable monochromatic bright THz-Wave source. Such a development of efficient and wide tunable THz-Wave source depends on discovery of novel brilliant nonlinear crystal. Important factors of a nonlinear crystal for THz-Wave Generation are, 1. High nonlinearity and 2. Good transparency at THz frequency region. Unfortunately, many nonlinear crystals have strong absorption at THz frequency region. The fact limits efficient and wide tunable THz-Wave Generation. Here, we show that Cherenkov radiation with Waveguide structure is an effective strategy for achieving efficient and extremely wide tunable THz-Wave source. We fabricated MgO-doped lithium niobate slab Waveguide with 3.8 μm of thickness and demonstrated difference frequency Generation of THz-Wave Generation with Cherenkov phase matching. Extremely frequency-widened THz-Wave Generation, from 0.1 to 7.2 THz, without no structural dips successfully obtained. The tuning frequency range of Waveguided Cherenkov radiation source was extremely widened compare to that of injection seeded-Terahertz Parametric Generator. The tuning range obtained in this work for THz-Wave Generation using lithium niobate crystal was the widest value in our knowledge. The highest THz-Wave energy obtained was about 3.2 pJ, and the energy conversion efficiency was about 10-5 %. The method can be easily applied for many conventional nonlinear crystals, results in realizing simple, reasonable, compact, high efficient and ultra broad band THz-Wave sources.
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efficient cherenkov type phase matched widely tunable terahertz Wave Generation via an optimized pump beam shape
Applied Physics Express, 2009Co-Authors: Takayuki Shibuya, Takuya Akiba, Koji Suizu, Toshihiro Tsutsui, Kodo KawaseAbstract:We demonstrated a Cherenkov-type phase-matching method for monochromatic THz-Wave Generation using the difference frequency Generation process with a lithium niobate crystal. In Cherenkov-type phase-matching process, when the bulk lithium niobate crystal is used, the beam diameter of pump Waves causes the phase mismatching for generating THz-Wave. We decreased the phase-mismatch by optimizing the pump beam shape with cylindrical lenses, and ensured high conversion efficiency especially in the high-frequency region. We successfully generated monochromatic THz Waves across the 0.2- to 4.0-THz range with a simple configuration.
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cherenkov phase matched monochromatic thz Wave Generation using difference frequency Generation with a lithium niobate crystal
Optics Express, 2008Co-Authors: Koji Suizu, Takuya Akiba, Takayuki Shibuya, Toshihiro Tutui, Chiko Otani, Kodo KawaseAbstract:We demonstrated a Cherenkov phase-matching method for monochromatic THz-Wave Generation using the difference frequency Generation process with a lithium niobate crystal, which resulted in high conversion efficiency and wide tunability. We successfully generated monochromatic THz Waves across the range 0.2–3.0 THz. We obtained efficient energy conversion in the low frequency region below 0.5 THz, and achieved a flat tuning spectrum by varying the pumping Wavelength during THz-Wave tuning.
