Although broadband sideband generation has been observed in certain crystals and in chemical-vapor-deposition (CVD) diamond using stimulated Raman scattering (SRS) with nanosecond and picosecond lasers, researchers at Texas A&M University (College Station, TX) have now observed broadband generation in diamond using femtosecond laser pulses—an important move toward generating broad-spectrum, subfemtosecond light waveforms in solids. These subfemtosecond light waves have applications in ultrafast science and technology.
When the researchers apply a Stokes pulse (630 nm) and a pump pulse (584 nm) to a 500-µm-thick diamond, up to 18 multicolored beams are generated. Interference measurements confirm that the process creates mutually coherent sidebands; the researchers postulate that a single-cycle, 0.5-fs-wide pulse could be obtained with proper phase matching of the generated beams. When three beams are used with the sample in a boxed coherent anti-Stokes Raman scattering configuration, a two-dimensional array of multicolored beams is produced through SRS, four-wave mixing, and six-wave mixing. The researchers are working to optimize the broadband generation process by optimizing the input wavelengths and the optics that couple the signals into the diamond, and by using a thicker diamond sample for increased Raman gain. Contact Miaochan Zhi at [email protected].