Use Of Difference-frequency Generation Research Articles

Theoretical Exploration of Terahertz Single-Photon Detection and Imaging by Nonlinear Optical Frequency Up-Conversion

Terahertz single-photon detection and imaging have attracted full attention recently. Nonlinear optical frequency up-conversion is a promising technique that can be expected to satisfy this demand thanks to its high sensitivity and fast response. In this paper, theoretical analysis and numerical calculations based on the organic salt 4′-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST) crystal were performed to show that the optimization of the detection of terahertz is different from that of the generation of terahertz, including the use of difference-frequency generation (DFG) technique, the larger thickness of the crystal, and especially the selection of the polarization direction of the pumping laser. For two different polarization configurations, the photons of the up-converted signal light both can be amplified compared with the number of incident terahertz photons under some optimal designs of the nonlinear frequency conversion process. Therefore, terahertz single-photon detection can be realized with single-photon detectors (SPDs) or even possibly with ordinary avalanche photodiodes (APDs). Furthermore, for terahertz single-photon imaging, the frequency up-conversion with the pumping laser polarized along b-axis of DAST crystal has a better performance, which is rarely used in terahertz generation.

All-optical stabilization of carrier-envelope phase by use of difference frequency generation with seeded amplification of colored conical emission

We stabilized the carrier-envelope phase of pulses emitted by a femtosecond regenerative amplifier through difference frequency generation between pump and seeded amplification of colored conical emission. Seeded amplification of colored conical emission was induced by modulational instability in the second harmonic generation with a supercontinuum injected and amplified. As a consequence, it inherited the origin phase of the pump pulse. After difference frequency with the pump pulses, the generated tunable idler pulses were carrier-envelope phase stabilized, which was verified with a simple and robust spectral interference setup.

Self-stabilization of carrier-envelope offset phase by use of difference-frequency generation

Self-stabilized carrier-envelope offset phase is achieved by use of difference-frequency (DF) generation. The spectrum from a Ti:sapphire oscillator is broadened in a photonic crystal fiber, and a DF (900 nm) between the blue component (490 nm) and the infrared component (1080 nm) is generated. The beat signal between the fundamental and the DF signal is clearly observed. The wavelength of the DF signal can be tuned down to 780 nm, and hence the signal can be used for injection seeding of a Ti:sapphire oscillator.

Flexible and rapidly configurable femtosecond pulse generation in the mid-IR.

We demonstrate a new experimental approach for flexible femtosecond pulse generation in the mid-IR by use of difference-frequency generation from two tightly synchronized Ti:sapphire lasers. The resultant mid-IR pulse train can be easily tuned, with an adjustable repetition frequency up to 100 MHz, a pulse energy of approximately 1.5 x 10(-13) J, and an intensity noise similar to that of the Ti:sapphire. Rapid switching of the mid-IR wavelength and programmable amplitude modulation are achieved by precision setting of the time delay between two original pulses.

Division by 3 of optical frequencies by use of difference-frequency generation in noncritically phase-matched RbTiOAsO_4

A new scheme for coherently connecting optical frequencies in a 3:1 ratio has been demonstrated. To phase lock a Nd:YAG laser at 1064 nm with a CO overtone laser at 3192 nm, we generated their difference frequency in RbTiOAsO(4) (RTA) and beat it against the second harmonic of 3192 nm that was generated in AgGaSe(2).

Generation of intense sub-picosecond pulses in the mid-infrared

We describe the use of difference-frequency generation, by mixing two intense femtosecond pulses in a 5-mm long BBO crystal, to generate high power 2.5 μm pulses with a duration of less than 0.5 ps. The pulses are generated by mixing the output of an amplified CPM laser with an amplified part of a continuum. The generated pulses have an energy of 4 μJ which amounts to a photon-conversion efficiency of 5 percent.