Search

A novel scheme to realize widely tunable optical parametric oscillator (OPO) based on an x-cut KTP crystal is demonstrated. The tuning range from 1572.5 nm to 1697 nm was enabled by a 1:1 imaging optical system with a variable deflection mirror to couple the 1064-nm laser pulses into the OPO cavity in the noncollinear phase-matching (PM) configuration. Benefitting from varying the pump direction rather than the cavity axis, the OPO cavity was unaffected so that the stability of the output signal energy and beam direction could be maintained, which greatly facilitates subsequent applications. The change of pump threshold, output energy, linewidth and temporal pulse shapes during wavelength tuning were also discussed.

A novel scheme to realize widely tunable optical parametric oscillator (OPO) based on an x-cut KTP crystal is demonstrated. The tuning range from 1572.5 nm to 1697 nm was enabled by a 1:1 imaging optical system with a variable deflection mirror to couple the 1064-nm laser pulses into the OPO cavity in the noncollinear phase-matching (PM) configuration. Benefitting from varying the pump direction rather than the cavity axis, the OPO cavity was unaffected so that the stability of the output signal energy and beam direction could be maintained, which greatly facilitates subsequent applications. The change of pump threshold, output energy, linewidth and temporal pulse shapes during wavelength tuning were also discussed. [ABSTRACT FROM AUTHOR]

We have succeeded in developing tunable picosecond terahertz (THz)-wave parametric oscillators (ps-TPOs) by employing a noncollinear pump-enhanced signal-resonant cavity. As a parametric gain medium, we use two different shapes of unpoled, 5 mol% MgO-doped lithium niobate (MgO:LiNbO3) crystal: 1) a rectangle for Si-prism output-coupler technique and 2) a trapezoid for surface-emitted configuration. Unlike conventional nanosecond TPOs (ns-TPOs), these ps-TPOs are synchronously pumped by a mode-locked 1.5-ps Ti:sapphire laser operating at 780 nm. To overcome the high pump threshold due to the strong absorption by MgO:LiNbO3 in the THz region, we employ a pump-enhanced cavity which is carefully designed for the noncollinear dual resonance of both pump and signal waves. By slightly translating the position of one of the ps-TPO cavity mirrors, we experimentally find that the THz-wave peak frequency is continuously tunable from 0.9 to 3.3 THz, approximately, with the average output power of dozens of nanowatts. In all the above tuning range, especially above 2 THz, the THz-wave output of the surface-emitting ps-TPO using the trapezoidal MgO:LiNbO3 crystal is enhanced several times more than that of the Si-prism-coupled ps-TPO using the rectangular MgO:LiNbO 3 crystal due to the suppression of the absorption loss in MgO:LiNbO3. [ABSTRACT FROM PUBLISHER]

A high-powered pulsed terahertz (THz)-wave has been parametrically generated via a surface-emitted THz-wave parametric oscillator (TPO). The effective parametric gain length under the noncollinear phase matching condition was calculated for optimization of the parameters of the TPO. A large volume crystal of MgO:LiNbO3 was used as the gain medium. THz-wave radiation covering a frequency range from 0.87 to 2.73 THz was obtained. The average power of the THz-wave was 9.12 µW at 1.75 THz when the pump energy was 94 mJ, corresponding to an energy conversion efficiency of about 9.7 x 10-6 and a photon conversion efficiency of about 0.156%. The THz-wave power in our experiments is high enough for practical applications to spectrum analysis and imaging. [ABSTRACT FROM AUTHOR]

Abstract: A high-powered tunable terahertz wave (THz-wave) has been parametrically generated via a surface-emitted THz-wave parametric oscillator (TPO) pumped by a multi-longitudinal-mode Q-switched Nd:YAG laser. The effective parametric gain length was enlarged by employing two MgO:LiNbO3 crystals. The tunable THz-wave radiation from 0.8 to 2.8THz was realized via varying phase-matching angle between the pump wave and the Stokes wave. The maximum THz-wave radiation was 173.9nJ/pulse at 1.7THz as the pump energy was 82mJ, corresponding to an energy conversion efficiency of about 2.12×10−6 and a photon conversion efficiency of about 0.035%. The first-order, the second-order and the third-order Stokes waves were observed during the experiments. [Copyright &y& Elsevier]