FEL & Utilization Section

Development of facilities for terahertz-infrared (IR-THz) spectroscopy

The IR-FEL beam has been transported through 52 meters to reach the user laboratory in the adjacent building, where initial trial experiments have been stared for the utilization of the IR-FEL light for doing materials research. Figure 6 shows the test bench set-up where these experiments are in progress.

Figure 6: The experimental arrangement showing the optical components, the magneto-optical cryostat and the pyroelectric detectors being used for the trial experiments using the IR-FEL

Figure 7: Experimental set-up for IR-FEL and laboratory source based frequency domain spectroscopy studies at low temperatures and in high magneic fields.

Figure 8: Experimental set-up for doing THz-TDS measurements at low temperatures.

For complementary studies, a terahertz time domain spectroscopy (THz-TDS) set-up has been established for the frequency range 0.1 to 3 THz frequency (3 mm to 100 μm wavelength) range. Similar to the frequency domain spectroscopy set-up, the THz-TDS set-up is also conjugated with a magneto-optical cryostat system that provides low temperature (1.5 - 300 K) and high magnetic field sample environment (see figure 8). The THz radiation is produced by a Bi-doped GaAs photoconductive antenna pumped using a 1030 nm DPSS Laser giving 96 fs duration pulses at a repetition rate of 76 MHz). The real and imaginary pars of the optical constants of materials can be directly measured in the THz range using this set-up, without using mathematical transformations. The set-up can also do NIR-pump THz-probe measurements. User experiments have been started using the above experimental set-ups, and users from UGC-DAE-CSR Indore, IIT Bombay, IIT Indore, NIT, Jalandhar, MVGR Collage of Engineering Hyderabad, etc. have performed their studies based on the same.