Gapless tunable intense terahertz pulse generation in strained diamond

We demonstrate collinear phase matching of transient coherent Stokes Raman scattering (CSRS) in strained diamond, enabling generation of intense, high-quality, femtosecond THz pulses over a gapless frequency band from 5 to beyond 15 THz. Our experimental results confirm this mechanism, supported by the theoretical calculations that agrees well with measurements. The theoretical model also provides a clear picture on how the input pulses should be adjusted to optimize the THz output from a diamond of given length.