Abstract

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.

© 2009 Optical Society of America

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  1. G. D. Boyd, T. J. Bridges, C. K. N. Patel, and E. Buehler, " Phase-matched submillimeter wave generation by difference-frequency mixing in ZnGeP2," Appl. Phys. Lett. 21, 553-555 (1972).
    [CrossRef]
  2. A. Rice, Y. Jin, X. F. Ma, X. C. Zhang, D. Bliss, J. Larkin, and M. Alexander, "Terahertz optical rectification from <110> zinc-blende crystals," Appl. Phys. Lett. 64, 1324-1326 (1994).
    [CrossRef]
  3. W. Shi, Y. J. Ding, N. Fernelius, and K. Vodopyanov, "Efficient, tunable, and coherent 0.18-5.27-THz source based on GaSe crystal," Opt. Lett. 27, 1454-1456 (2002).
    [CrossRef]
  4. T. Tanabe, K. Suto, J. Nishizawa, K. Saito, and T. Kimura, "Tunable terahertz wave generation in the 3- to 7-THz region from GaP," Appl. Phys. Lett. 83, 237-239 (2003).
    [CrossRef]
  5. Y. Avetisyan, Y. Sasaki, and H. Ito, "Analysis of THz-wave surface-emitted difference-frequency generation in periodically poled lithium niobate waveguide," Appl. Phys. B 73, 511-514 (2001).
  6. D. H. Auston, K. P. Cheung, J. A. Valdmanis, and D. A. Kleinman, "Cherenkov radiation from femtosecond optical pulses in electro-optic media," Phys. Rev. Lett. 53, 1555-1558 (1984).
    [CrossRef]
  7. D. A. Kleinman and D. H. Auston, "Theory of electro-optic shock radiation in nonlinear optical media," IEEE J. Quantum Electron. 20, 964-970 (1984).
    [CrossRef]
  8. J. Hebling, G. Almasi, I. Kozma, and J. Kuhl, "Velocity matching by pulse front tilting for large area THz-pulse generation," Opt. Express 10, 1161-1166 (2002).
    [PubMed]
  9. J. K. Wahlstrand and R. Merlin, "Cherenkov radiation emitted by ultrafast laser pulses and the generation of coherent polaritons," Phys. Rev. B 68, 054301 (2003).
    [CrossRef]
  10. K.-L. Yeh, M. C. Hoffmann, J. Hebling, and K. A. Nelson, "Generation of 10 ?J ultrashort THz pulses by optical rectification," Appl. Phys. Lett. 90, 171121 (2007).
    [CrossRef]
  11. S. B. Bodrov, A. N. Stepanov, M. I. Bakunov, B. V. Shishkin, I. E. Ilyakov, and R. A. Akhmedzhanov, "Highly efficient optical-to-terahertz conversion in a sandwich structure with LiNbO3 core," Opt. Express 17, 1871-1879 (2009).
    [CrossRef] [PubMed]
  12. K. Suizu, T. Tutui, T. Shibuya, T. Akiba, and K. Kawase, "Cherenkov phase-matched monochromatic THz-wave generation using difference frequency generation with lithium niobate crystal," Opt. Express 16, 7493-7498 (2008).
    [CrossRef] [PubMed]
  13. T. Shibuya, T. Tsutsui, K. Suizu, T. Akiba, and K. Kawase, "Efficient Cherenkov-Type Phase-Matched Widely Tunable THz-Wave Generation via an Optimized Pump Beam Shape," Appl. Phys. Express 2, 032302 (2009).
    [CrossRef]
  14. D. E. Zelmon, D. L. Small, and D. Jundt, "Infrared corrected Sellmeier coefficients for congruently grown lithium niobate and 5 mol. % magnesium oxide-doped lithium niobate," J. Opt. Soc. Am. B 14, 3319-3322 (1997).
    [CrossRef]
  15. K. Kawase, H. Minamide, K. Imai, J. Shikata, and H. Ito, "Injection-seeded terahertz-wave parametric generator with wide tenability," Appl. Phys. Lett. 80, 195-197 (2002).
    [CrossRef]
  16. Y. Sasaki, H. Yokoyama, and H. Ito, "Surface-emitted continuous-wave terahertz radiation using periodically poled lithium niobate," Electron. Lett. 41, 712-713 (2005).
    [CrossRef]

2009 (2)

S. B. Bodrov, A. N. Stepanov, M. I. Bakunov, B. V. Shishkin, I. E. Ilyakov, and R. A. Akhmedzhanov, "Highly efficient optical-to-terahertz conversion in a sandwich structure with LiNbO3 core," Opt. Express 17, 1871-1879 (2009).
[CrossRef] [PubMed]

T. Shibuya, T. Tsutsui, K. Suizu, T. Akiba, and K. Kawase, "Efficient Cherenkov-Type Phase-Matched Widely Tunable THz-Wave Generation via an Optimized Pump Beam Shape," Appl. Phys. Express 2, 032302 (2009).
[CrossRef]

2008 (1)

2007 (1)

K.-L. Yeh, M. C. Hoffmann, J. Hebling, and K. A. Nelson, "Generation of 10 ?J ultrashort THz pulses by optical rectification," Appl. Phys. Lett. 90, 171121 (2007).
[CrossRef]

2005 (1)

Y. Sasaki, H. Yokoyama, and H. Ito, "Surface-emitted continuous-wave terahertz radiation using periodically poled lithium niobate," Electron. Lett. 41, 712-713 (2005).
[CrossRef]

2003 (2)

J. K. Wahlstrand and R. Merlin, "Cherenkov radiation emitted by ultrafast laser pulses and the generation of coherent polaritons," Phys. Rev. B 68, 054301 (2003).
[CrossRef]

T. Tanabe, K. Suto, J. Nishizawa, K. Saito, and T. Kimura, "Tunable terahertz wave generation in the 3- to 7-THz region from GaP," Appl. Phys. Lett. 83, 237-239 (2003).
[CrossRef]

2002 (3)

2001 (1)

Y. Avetisyan, Y. Sasaki, and H. Ito, "Analysis of THz-wave surface-emitted difference-frequency generation in periodically poled lithium niobate waveguide," Appl. Phys. B 73, 511-514 (2001).

1997 (1)

1994 (1)

A. Rice, Y. Jin, X. F. Ma, X. C. Zhang, D. Bliss, J. Larkin, and M. Alexander, "Terahertz optical rectification from <110> zinc-blende crystals," Appl. Phys. Lett. 64, 1324-1326 (1994).
[CrossRef]

1984 (2)

D. H. Auston, K. P. Cheung, J. A. Valdmanis, and D. A. Kleinman, "Cherenkov radiation from femtosecond optical pulses in electro-optic media," Phys. Rev. Lett. 53, 1555-1558 (1984).
[CrossRef]

D. A. Kleinman and D. H. Auston, "Theory of electro-optic shock radiation in nonlinear optical media," IEEE J. Quantum Electron. 20, 964-970 (1984).
[CrossRef]

1972 (1)

G. D. Boyd, T. J. Bridges, C. K. N. Patel, and E. Buehler, " Phase-matched submillimeter wave generation by difference-frequency mixing in ZnGeP2," Appl. Phys. Lett. 21, 553-555 (1972).
[CrossRef]

Akiba, T.

T. Shibuya, T. Tsutsui, K. Suizu, T. Akiba, and K. Kawase, "Efficient Cherenkov-Type Phase-Matched Widely Tunable THz-Wave Generation via an Optimized Pump Beam Shape," Appl. Phys. Express 2, 032302 (2009).
[CrossRef]

K. Suizu, T. Tutui, T. Shibuya, T. Akiba, and K. Kawase, "Cherenkov phase-matched monochromatic THz-wave generation using difference frequency generation with lithium niobate crystal," Opt. Express 16, 7493-7498 (2008).
[CrossRef] [PubMed]

Alexander, M.

A. Rice, Y. Jin, X. F. Ma, X. C. Zhang, D. Bliss, J. Larkin, and M. Alexander, "Terahertz optical rectification from <110> zinc-blende crystals," Appl. Phys. Lett. 64, 1324-1326 (1994).
[CrossRef]

Almasi, G.

Auston, D. H.

D. H. Auston, K. P. Cheung, J. A. Valdmanis, and D. A. Kleinman, "Cherenkov radiation from femtosecond optical pulses in electro-optic media," Phys. Rev. Lett. 53, 1555-1558 (1984).
[CrossRef]

D. A. Kleinman and D. H. Auston, "Theory of electro-optic shock radiation in nonlinear optical media," IEEE J. Quantum Electron. 20, 964-970 (1984).
[CrossRef]

Avetisyan, Y.

Y. Avetisyan, Y. Sasaki, and H. Ito, "Analysis of THz-wave surface-emitted difference-frequency generation in periodically poled lithium niobate waveguide," Appl. Phys. B 73, 511-514 (2001).

Bakunov, M. I.

Bliss, D.

A. Rice, Y. Jin, X. F. Ma, X. C. Zhang, D. Bliss, J. Larkin, and M. Alexander, "Terahertz optical rectification from <110> zinc-blende crystals," Appl. Phys. Lett. 64, 1324-1326 (1994).
[CrossRef]

Bodrov, S. B.

Boyd, G. D.

G. D. Boyd, T. J. Bridges, C. K. N. Patel, and E. Buehler, " Phase-matched submillimeter wave generation by difference-frequency mixing in ZnGeP2," Appl. Phys. Lett. 21, 553-555 (1972).
[CrossRef]

Bridges, T. J.

G. D. Boyd, T. J. Bridges, C. K. N. Patel, and E. Buehler, " Phase-matched submillimeter wave generation by difference-frequency mixing in ZnGeP2," Appl. Phys. Lett. 21, 553-555 (1972).
[CrossRef]

Buehler, E.

G. D. Boyd, T. J. Bridges, C. K. N. Patel, and E. Buehler, " Phase-matched submillimeter wave generation by difference-frequency mixing in ZnGeP2," Appl. Phys. Lett. 21, 553-555 (1972).
[CrossRef]

Cheung, K. P.

D. H. Auston, K. P. Cheung, J. A. Valdmanis, and D. A. Kleinman, "Cherenkov radiation from femtosecond optical pulses in electro-optic media," Phys. Rev. Lett. 53, 1555-1558 (1984).
[CrossRef]

Ding, Y. J.

Fernelius, N.

Hebling, J.

K.-L. Yeh, M. C. Hoffmann, J. Hebling, and K. A. Nelson, "Generation of 10 ?J ultrashort THz pulses by optical rectification," Appl. Phys. Lett. 90, 171121 (2007).
[CrossRef]

J. Hebling, G. Almasi, I. Kozma, and J. Kuhl, "Velocity matching by pulse front tilting for large area THz-pulse generation," Opt. Express 10, 1161-1166 (2002).
[PubMed]

Hoffmann, M. C.

K.-L. Yeh, M. C. Hoffmann, J. Hebling, and K. A. Nelson, "Generation of 10 ?J ultrashort THz pulses by optical rectification," Appl. Phys. Lett. 90, 171121 (2007).
[CrossRef]

Imai, K.

K. Kawase, H. Minamide, K. Imai, J. Shikata, and H. Ito, "Injection-seeded terahertz-wave parametric generator with wide tenability," Appl. Phys. Lett. 80, 195-197 (2002).
[CrossRef]

Ito, H.

Y. Sasaki, H. Yokoyama, and H. Ito, "Surface-emitted continuous-wave terahertz radiation using periodically poled lithium niobate," Electron. Lett. 41, 712-713 (2005).
[CrossRef]

K. Kawase, H. Minamide, K. Imai, J. Shikata, and H. Ito, "Injection-seeded terahertz-wave parametric generator with wide tenability," Appl. Phys. Lett. 80, 195-197 (2002).
[CrossRef]

Y. Avetisyan, Y. Sasaki, and H. Ito, "Analysis of THz-wave surface-emitted difference-frequency generation in periodically poled lithium niobate waveguide," Appl. Phys. B 73, 511-514 (2001).

Jin, Y.

A. Rice, Y. Jin, X. F. Ma, X. C. Zhang, D. Bliss, J. Larkin, and M. Alexander, "Terahertz optical rectification from <110> zinc-blende crystals," Appl. Phys. Lett. 64, 1324-1326 (1994).
[CrossRef]

Jundt, D.

Kawase, K.

T. Shibuya, T. Tsutsui, K. Suizu, T. Akiba, and K. Kawase, "Efficient Cherenkov-Type Phase-Matched Widely Tunable THz-Wave Generation via an Optimized Pump Beam Shape," Appl. Phys. Express 2, 032302 (2009).
[CrossRef]

K. Suizu, T. Tutui, T. Shibuya, T. Akiba, and K. Kawase, "Cherenkov phase-matched monochromatic THz-wave generation using difference frequency generation with lithium niobate crystal," Opt. Express 16, 7493-7498 (2008).
[CrossRef] [PubMed]

K. Kawase, H. Minamide, K. Imai, J. Shikata, and H. Ito, "Injection-seeded terahertz-wave parametric generator with wide tenability," Appl. Phys. Lett. 80, 195-197 (2002).
[CrossRef]

Kimura, T.

T. Tanabe, K. Suto, J. Nishizawa, K. Saito, and T. Kimura, "Tunable terahertz wave generation in the 3- to 7-THz region from GaP," Appl. Phys. Lett. 83, 237-239 (2003).
[CrossRef]

Kleinman, D. A.

D. H. Auston, K. P. Cheung, J. A. Valdmanis, and D. A. Kleinman, "Cherenkov radiation from femtosecond optical pulses in electro-optic media," Phys. Rev. Lett. 53, 1555-1558 (1984).
[CrossRef]

D. A. Kleinman and D. H. Auston, "Theory of electro-optic shock radiation in nonlinear optical media," IEEE J. Quantum Electron. 20, 964-970 (1984).
[CrossRef]

Kozma, I.

Kuhl, J.

Larkin, J.

A. Rice, Y. Jin, X. F. Ma, X. C. Zhang, D. Bliss, J. Larkin, and M. Alexander, "Terahertz optical rectification from <110> zinc-blende crystals," Appl. Phys. Lett. 64, 1324-1326 (1994).
[CrossRef]

Ma, X. F.

A. Rice, Y. Jin, X. F. Ma, X. C. Zhang, D. Bliss, J. Larkin, and M. Alexander, "Terahertz optical rectification from <110> zinc-blende crystals," Appl. Phys. Lett. 64, 1324-1326 (1994).
[CrossRef]

Merlin, R.

J. K. Wahlstrand and R. Merlin, "Cherenkov radiation emitted by ultrafast laser pulses and the generation of coherent polaritons," Phys. Rev. B 68, 054301 (2003).
[CrossRef]

Minamide, H.

K. Kawase, H. Minamide, K. Imai, J. Shikata, and H. Ito, "Injection-seeded terahertz-wave parametric generator with wide tenability," Appl. Phys. Lett. 80, 195-197 (2002).
[CrossRef]

Nelson, K. A.

K.-L. Yeh, M. C. Hoffmann, J. Hebling, and K. A. Nelson, "Generation of 10 ?J ultrashort THz pulses by optical rectification," Appl. Phys. Lett. 90, 171121 (2007).
[CrossRef]

Nishizawa, J.

T. Tanabe, K. Suto, J. Nishizawa, K. Saito, and T. Kimura, "Tunable terahertz wave generation in the 3- to 7-THz region from GaP," Appl. Phys. Lett. 83, 237-239 (2003).
[CrossRef]

Patel, C. K. N.

G. D. Boyd, T. J. Bridges, C. K. N. Patel, and E. Buehler, " Phase-matched submillimeter wave generation by difference-frequency mixing in ZnGeP2," Appl. Phys. Lett. 21, 553-555 (1972).
[CrossRef]

Rice, A.

A. Rice, Y. Jin, X. F. Ma, X. C. Zhang, D. Bliss, J. Larkin, and M. Alexander, "Terahertz optical rectification from <110> zinc-blende crystals," Appl. Phys. Lett. 64, 1324-1326 (1994).
[CrossRef]

Saito, K.

T. Tanabe, K. Suto, J. Nishizawa, K. Saito, and T. Kimura, "Tunable terahertz wave generation in the 3- to 7-THz region from GaP," Appl. Phys. Lett. 83, 237-239 (2003).
[CrossRef]

Sasaki, Y.

Y. Sasaki, H. Yokoyama, and H. Ito, "Surface-emitted continuous-wave terahertz radiation using periodically poled lithium niobate," Electron. Lett. 41, 712-713 (2005).
[CrossRef]

Y. Avetisyan, Y. Sasaki, and H. Ito, "Analysis of THz-wave surface-emitted difference-frequency generation in periodically poled lithium niobate waveguide," Appl. Phys. B 73, 511-514 (2001).

Shi, W.

Shibuya, T.

T. Shibuya, T. Tsutsui, K. Suizu, T. Akiba, and K. Kawase, "Efficient Cherenkov-Type Phase-Matched Widely Tunable THz-Wave Generation via an Optimized Pump Beam Shape," Appl. Phys. Express 2, 032302 (2009).
[CrossRef]

K. Suizu, T. Tutui, T. Shibuya, T. Akiba, and K. Kawase, "Cherenkov phase-matched monochromatic THz-wave generation using difference frequency generation with lithium niobate crystal," Opt. Express 16, 7493-7498 (2008).
[CrossRef] [PubMed]

Shikata, J.

K. Kawase, H. Minamide, K. Imai, J. Shikata, and H. Ito, "Injection-seeded terahertz-wave parametric generator with wide tenability," Appl. Phys. Lett. 80, 195-197 (2002).
[CrossRef]

Shishkin, B. V.

Small, D. L.

Stepanov, A. N.

Suizu, K.

T. Shibuya, T. Tsutsui, K. Suizu, T. Akiba, and K. Kawase, "Efficient Cherenkov-Type Phase-Matched Widely Tunable THz-Wave Generation via an Optimized Pump Beam Shape," Appl. Phys. Express 2, 032302 (2009).
[CrossRef]

K. Suizu, T. Tutui, T. Shibuya, T. Akiba, and K. Kawase, "Cherenkov phase-matched monochromatic THz-wave generation using difference frequency generation with lithium niobate crystal," Opt. Express 16, 7493-7498 (2008).
[CrossRef] [PubMed]

Suto, K.

T. Tanabe, K. Suto, J. Nishizawa, K. Saito, and T. Kimura, "Tunable terahertz wave generation in the 3- to 7-THz region from GaP," Appl. Phys. Lett. 83, 237-239 (2003).
[CrossRef]

Tanabe, T.

T. Tanabe, K. Suto, J. Nishizawa, K. Saito, and T. Kimura, "Tunable terahertz wave generation in the 3- to 7-THz region from GaP," Appl. Phys. Lett. 83, 237-239 (2003).
[CrossRef]

Tsutsui, T.

T. Shibuya, T. Tsutsui, K. Suizu, T. Akiba, and K. Kawase, "Efficient Cherenkov-Type Phase-Matched Widely Tunable THz-Wave Generation via an Optimized Pump Beam Shape," Appl. Phys. Express 2, 032302 (2009).
[CrossRef]

Tutui, T.

Valdmanis, J. A.

D. H. Auston, K. P. Cheung, J. A. Valdmanis, and D. A. Kleinman, "Cherenkov radiation from femtosecond optical pulses in electro-optic media," Phys. Rev. Lett. 53, 1555-1558 (1984).
[CrossRef]

Vodopyanov, K.

Wahlstrand, J. K.

J. K. Wahlstrand and R. Merlin, "Cherenkov radiation emitted by ultrafast laser pulses and the generation of coherent polaritons," Phys. Rev. B 68, 054301 (2003).
[CrossRef]

Yeh, K.-L.

K.-L. Yeh, M. C. Hoffmann, J. Hebling, and K. A. Nelson, "Generation of 10 ?J ultrashort THz pulses by optical rectification," Appl. Phys. Lett. 90, 171121 (2007).
[CrossRef]

Yokoyama, H.

Y. Sasaki, H. Yokoyama, and H. Ito, "Surface-emitted continuous-wave terahertz radiation using periodically poled lithium niobate," Electron. Lett. 41, 712-713 (2005).
[CrossRef]

Zelmon, D. E.

Zhang, X. C.

A. Rice, Y. Jin, X. F. Ma, X. C. Zhang, D. Bliss, J. Larkin, and M. Alexander, "Terahertz optical rectification from <110> zinc-blende crystals," Appl. Phys. Lett. 64, 1324-1326 (1994).
[CrossRef]

Appl. Phys. B (1)

Y. Avetisyan, Y. Sasaki, and H. Ito, "Analysis of THz-wave surface-emitted difference-frequency generation in periodically poled lithium niobate waveguide," Appl. Phys. B 73, 511-514 (2001).

Appl. Phys. Express (1)

T. Shibuya, T. Tsutsui, K. Suizu, T. Akiba, and K. Kawase, "Efficient Cherenkov-Type Phase-Matched Widely Tunable THz-Wave Generation via an Optimized Pump Beam Shape," Appl. Phys. Express 2, 032302 (2009).
[CrossRef]

Appl. Phys. Lett. (5)

K. Kawase, H. Minamide, K. Imai, J. Shikata, and H. Ito, "Injection-seeded terahertz-wave parametric generator with wide tenability," Appl. Phys. Lett. 80, 195-197 (2002).
[CrossRef]

T. Tanabe, K. Suto, J. Nishizawa, K. Saito, and T. Kimura, "Tunable terahertz wave generation in the 3- to 7-THz region from GaP," Appl. Phys. Lett. 83, 237-239 (2003).
[CrossRef]

G. D. Boyd, T. J. Bridges, C. K. N. Patel, and E. Buehler, " Phase-matched submillimeter wave generation by difference-frequency mixing in ZnGeP2," Appl. Phys. Lett. 21, 553-555 (1972).
[CrossRef]

A. Rice, Y. Jin, X. F. Ma, X. C. Zhang, D. Bliss, J. Larkin, and M. Alexander, "Terahertz optical rectification from <110> zinc-blende crystals," Appl. Phys. Lett. 64, 1324-1326 (1994).
[CrossRef]

K.-L. Yeh, M. C. Hoffmann, J. Hebling, and K. A. Nelson, "Generation of 10 ?J ultrashort THz pulses by optical rectification," Appl. Phys. Lett. 90, 171121 (2007).
[CrossRef]

Electron. Lett. (1)

Y. Sasaki, H. Yokoyama, and H. Ito, "Surface-emitted continuous-wave terahertz radiation using periodically poled lithium niobate," Electron. Lett. 41, 712-713 (2005).
[CrossRef]

IEEE J. Quantum Electron. (1)

D. A. Kleinman and D. H. Auston, "Theory of electro-optic shock radiation in nonlinear optical media," IEEE J. Quantum Electron. 20, 964-970 (1984).
[CrossRef]

J. Opt. Soc. Am. B (1)

Opt. Express (3)

Opt. Lett. (1)

Phys. Rev. B (1)

J. K. Wahlstrand and R. Merlin, "Cherenkov radiation emitted by ultrafast laser pulses and the generation of coherent polaritons," Phys. Rev. B 68, 054301 (2003).
[CrossRef]

Phys. Rev. Lett. (1)

D. H. Auston, K. P. Cheung, J. A. Valdmanis, and D. A. Kleinman, "Cherenkov radiation from femtosecond optical pulses in electro-optic media," Phys. Rev. Lett. 53, 1555-1558 (1984).
[CrossRef]

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Figures (3)

Fig. 1.
Fig. 1.

Cherenkov angle for various nonlinear crystals (pink collared diamonds) and calculated critical angle between a crystal and a clad. Black, aqua, green, blue and red curve represent Air, polyethylene, diamond, Si and Ge as a clad material, respectively. A total internal reflection occurs below the curve. Inset shows a schematic of Cherenkov radiation and output coupling of a THz-frequency wave.

Fig. 2.
Fig. 2.

(a) Schematic of the lithium niobate waveguide device with Si prism array coupler. (b) THz-wave detection experimental setup.

Fig.3
Fig.3

THz-frequency spectrum of waveguided Cherenkov radiation. Black, red, blue and green curves represent l1 pumping wavelengths of 1250, 1300, 1350 and 1400 nm, respectively. An inset 3 shows a comparison of normalized tuning spectrum of the waveguided Cherenkov radiation source under 1250 nm pumping (solid curve) and is-TPG (dashed curve).

Equations (4)

Equations on this page are rendered with MathJax. Learn more.

cos θ crystal = λ THz n THz 2 L c = λ THz n THz λ 1 λ 2 ( n 1 λ 2 n 2 λ 1 ) n opt n THz
θ clad = π 2 β = π 2 arcsin ( n THz n clad sin ( α ) ) = π 2 arcsin ( n THz n clad sin ( π 2 θ crystal ) )
= π 2 arcsin ( n THz n clad sin ( π 2 arccos ( n 1 λ 2 n 2 λ 1 n THz ( λ 2 λ 1 ) ) ) )
= arccos ( n 1 λ 2 n 2 λ 1 n clad ( λ 2 λ 1 ) )

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