THz-radiation Generation from an Intracavity Saturable Bragg Reflector in a Magnetic Field

Abstract

We have demonstrated a new method to generate intense THz-radiation, up to a sub-microwatt level from a saturable Bragg reflector in a magnetic field. The saturable Bragg reflector is substituted in place of the end mirror in a femtosecond mode-locked Ti:sapphire laser pumped by an all-solid-state green laser.

THz radiation from GaAs surfaces with metallic nano-dot arrays under optical excitation

“…[1][2][3] The generation of THz radiation from the semiconductor surface has been understood by the surface field acceleration and the photo-Dember effect. [4,5] Thus, the characteristics of THz radiation depend on the surface defect density, the bulk carrier concentration and the mobility of the carriers of the semiconductors.…”

THz Radiation from Intracavity Saturable Bragg Reflector in Magnetic Field with Self-Started Mode-Locking by Strained Saturable Bragg Reflector

“…Previously, dye saturable absorbers were employed for selfstarting mode-locking in these intracavity THz-radiation generation systems. 6,7) However, the systems were bulky and relatively inconvenient to use. Recently, a new type of saturable absorber, the strained saturable Bragg reflector (SSBR), has been successfully developed for self-starting mode-locking with no focusing because of its very low saturation fluence of approximately 7 mJ/cm 2 .…”

“…The SSBR allows the construction of a more compact system and facilitates mode-locking of the Ti:sapphire laser with intracavity SBR to generate higher THz-radiation power. On the other hand, a magnetic field can be used not only to switch THz-radiation beams 9) but also to generate larger average THz-radiation power in the extra cavity 10) or intracavity 7) geometries. Here, we also discuss the characteristics of the intra cavity THz-radiation generation system with SBR as a function of magnetic field strength for the first time, to the best of our knowledge.…”

“…With a DBR mirror with an additional λ/2 layer of Al 0.25 Ga 0.75 As. The SBR, which serves as the THz emitter 6,7) is in the other arm of the z-folded cavity as the end mirror. Its Bragg reflector consists of 24 pairs of Al 0.33 Ga 0.67 As/AlAs λ/4 layers and a top λ/4 layer of AlGaAs including a single 10-nm-thick GaAs QW.…”

“…The THz-radiation detection system is the same as that described in our previous work. 6,7) The emitted THz radiation in the transmission direction was guided by the two parabolic mirrors directly to the InSb bolometer for detecting the THzradiation power or to the Fourier-transform polarizing interferometer for measurement of the THz-radiation spectrum.…”