10 THz Ultrafast Function Generator - generation of rectangular and triangular pulse trains-

We report the synthesis of arbitrary optical waveforms by manipulating the spectral phases of Raman sidebands with a wide frequency spacing line-by-line. Trains of rectangular and triangular pulses are stably produced at an ultrahigh repetition rate of 10.6229 THz, reminiscent of an ultrafast function generator.Comment: 7 Pages, 5 Figure

Freely designable optical frequency conversion in Raman-resonant four-wave-mixing process

Nonlinear optical processes are governed by the relative-phase relationships among the relevant electromagnetic fields in these processes. In this Report, we describe the physics of arbitrary manipulation of Raman-resonant four-wave-mixing process by artificial control of relative phases. As a typical example, we show freely designable optical-frequency conversions to extreme spectral regions, mid-infrared and vacuum-ultraviolet, with near-unity quantum efficiencies. Furthermore, we show that such optical-frequency conversions can be realized by using a surprisingly simple technology where transparent plates are placed in a nonlinear optical medium and their positions and thicknesses are adjusted precisely. In a numerical simulation assuming practically applicable parameters in detail, we demonstrate a single-frequency tunable laser that covers the whole vacuum-ultraviolet spectral range of 120 to 200 nm

Arbitrary manipulation of amplitude and phase of a set of highly discrete coherent spectra

We describe the attractive optical nature of highly discrete coherent spectra. We show that the relative amplitude and phase of such spectra can be almost arbitrarily manipulated by simply placing three fundamental optical elements—namely, a waveplate, polarizer, and dispersive plate—on an optical axis and then controlling their thicknesses. We also describe the relevant physical mechanism. Furthermore, as a typical application of this optical nature, we demonstrate arbitrary optical waveform generation in a numerical experiment, and we discuss its limitations as an optical-wave manipulation technology and how we can overcome these limitations

Coherent phonon induced optical modulation in semiconductors at terahertz frequencies

The coherent modulation of electronic and vibrational nonlinearities in atoms and molecular gases by intense few-cycle pulses has been used for high-harmonic generation in the soft X-ray and attosecond regime, as well as for Raman frequency combs that span multiple octaves from the Terahertz to Petahertz frequency regions. In principle, similar high-order nonlinear processes can be excited efficiently in solids and liquids on account of their high nonlinear polarizability densities. In this paper, we demonstrate the phononic modulation of the optical index of Si and GaAs for excitation and probing near their direct band gaps, respectively at ~3.4 eV and ~3.0 eV. The large amplitude coherent longitudinal optical polarization due to the excitation of longitudinal optical (LO) phonon of Si (001) and LO phonon-plasmon coupled modes in GaAs (001) excited by 10-fs laser pulses induces effective amplitude and phase modulation of the reflected probe light. The combined action of the amplitude and phase modulation in Si and GaAs generates phonon frequency combs with more than 100 and 60 THz bandwidth, respectively.Comment: 15 pages, 11 figure

Generation of five phase-locked harmonics by implementing a divide-by-three optical frequency divider

We report the generation of five phase-locked harmonics, f_1: 2403 nm, f_2: 1201 nm, f_3: 801 nm, f_4: 600 nm, and f_5: 480 nm with an exact frequency ratio of 1 : 2 : 3 : 4 : 5 by implementing a divide-by-three optical-frequency divider in the high harmonic generation process. All five harmonics are generated coaxially with high phase coherence in time and space, which are applicable for various practical uses.Comment: 6 pages, 6 figure

Generating arbitrary polarization states by manipulating the thicknesses of a pair of uniaxial birefringent plates

We report an optical method of generating arbitrary polarization states by manipulating the thicknesses of a pair of uniaxial birefringent plates, the optical axes of which are set at a crossing angle of {\pi}/4. The method has the remarkable feature of being able to generate a distribution of arbitrary polarization states in a group of highly discrete spectra without spatially separating the individual spectral components. The target polarization-state distribution is obtained as an optimal solution through an exploration. Within a realistic exploration range, a sufficient number of near-optimal solutions are found. This property is also reproduced well by a concise model based on a distribution of exploration points on a Poincar\'e sphere, showing that the number of near-optimal solutions behaves according to a power law with respect to the number of spectral components of concern. As a typical example of an application, by applying this method to a set of phase-locked highly discrete spectra, we numerically demonstrate the continuous generation of a vector-like optical electric field waveform, the helicity of which is alternated within a single optical cycle in the time domain.Comment: 7 pages, 5 figure

Generation of five phase-locked harmonics by implementing a divide-by-three optical frequency divider

We report the generation of five phase-locked harmonics, f1:2403  nm, f2:1201  nm, f:801  nm, f4:600  nm, and f5:480  nm with an exact frequency ratio of 1:2:3:4:5 by implementing a divide-by-three optical frequency divider in the high harmonic generation process. All five harmonics are generated coaxially with high phase coherence in time and space, which are applicable for various practical uses