Aniruddha S. Weling

A wideband coherent terahertz spectroscopy system using optical rectification and electro‐optic sampling

We present a scheme for exploiting the nonresonant second‐order nonlinearities in electro‐optic media to extend the bandwidth of coherent spectroscopy in the far‐infrared using ultrafast laser pulses. Using optical rectification and electro‐optic sampling in 〈110〉 ZnTe for the generation and coherent detection of freely propagating THz radiation, respectively, we have demonstrated spectral sensitivity beyond 3 THz. This was accomplished by achieving phase matching for both optical rectification and electro‐optic sampling over a broad range of THz frequencies.

Single-shot measurement of terahertz electromagnetic pulses by use of electro-optic sampling

We demonstrate a simple scheme for capturing the temporal waveforms of a freely propagating terahertz electromagnetic transient in a single shot. The method relies on electro-optic sampling in a noncollinear geometry for the terahertz radiation and the visible probe beam, coupled with multichannel detection. The approach provides time resolution that is comparable to that of conventional electro-optic sampling measurements.

Generation of tunable narrow‐band THz radiation from large aperture photoconducting antennas

We report a novel technique for the generation of tunable narrow‐band submillimeter wave electromagnetic radiation in free space. This is accomplished by mixing two linearly chirped optical pulses with a variable time delay on a biased large aperture GaAs photoconducting antenna. The center frequency of the THz radiation varies linearly with the delay between the two chirped pulses from dc to ∼1 THz.

Measurement of the vector character of electric fields by optical second-harmonic generation

We present a scheme for the determination of the vector nature of an electric field by optical second-harmonic generation. We demonstrate the technique by mapping the two-dimensional electric-field vector of a biased transmission line structure on silicon with a spatial resolution of ~10mum .

Homodyne detection of second-harmonic generation as a probe of the vector character of electric fields

Summary form only given. Ever since its first observation, optical second-harmonic generation (SHG) has been demonstrated to be a sensitive probe of electric fields in centrosymmetric media. Recent investigations have extended the capability of electric field-induced SHG (EFISH) to measure ultrafast electrical pulses and time-varying microwave electric-fields, with a time resolution limited only by the laser pulse duration. In this paper, we describe two interrelated advances in this method for probing electric fields: (1) a scheme for linearizing the relationship between the electric field and SHG intensity; and (2) an approach for determining the vector nature of the electric field. Measurements have been carried in silicon samples to demonstrate experimentally these improvements.

Tunable Photoconducting Emitters and Detectors of Free Space Terahertz Radiation

We describe a tunable terahertz beam system composed of narrowband photoconducting dipole emitters and detectors which can be used for nonlinear spectroscopy in the far-infrared.