ULTRAFAST PHOTONICS LABORATORY
Dept. of Applied Physics, DIAT, Pune
We are thankful for the funding received from DRDO, CARS Project Scheme and DIAT-Grant-in-Aid, which played an instrumental role in the development of Ultrafast Photonics Laboratory.
Design and Development of Ultrafast fiber lasers and amplifiers
UPL works on designing and developing modelocked fiber lasers utilizing different architectures. With the use of Polarization Maintained fibers and components, we try to eliminate the effects of environmental and thermal fluctuations on the modelocked pulse trace. The lab works on lasers in both normal and anomalous dispersion regimes. The work is primarily focused on 1060 nm in normal dispersion regime and eye safe (1.4 to 2.2 um) in anomlaous dispersion regime. Femtosecond lasers in 1550 nm regime are suited for THz generation and detection, with the aid of PCAs. The lab has already developed Yb-doped ultrafast fiber laser with output at 1060 nm and is tunable across the wavelength range of ~25 nm. The above said has been achieved using Artificial Saturable Absorbers and realized a Signal to Noise of Ratio of more than 75 dB. Currently, work is going on in the anomalous dispersion regime for THz applications, utilizing Figure of 8 and Figure of 9 oscillator architecture.​​​​​​​
Engineered Optical Fiber structures, probes and sensors
Light guiding optical fibers act as sensors or probes based on the geometry of the fiber modified to. One among these is tapering short section of fiber along its length where the tapered portion is sensitive to the environmental changes around it. These are used for chemical and bio-sensing. Apart from this the tip of the optical fiber can be tapered down to fine curvature tip or bulge it up to a spherical or spheroid structure. These modified fiber tips can be used as probes for imaging and sensor heads.
THz Time-domain Spectroscopy and Imaging
THz time domain spectroscopy is used to measure non-linear optical properties of various samples ranging from biological to semiconductors. UPL has a high-end customized THz TDS and Imaging system which collects data in the transmission and reflection modes simultaneously. The Imaging system has a resolution 0.1 mm and dedicated image processing module for high resolution THz imaging. TeraSmart TDS system present in UPL have a peak-to-peak voltages of 15V and 5V in transmission and reflection modes respectively, with a bandwidth upto 6 THz. The ultrafast fiber laser used in this setup to excite the Photo Conductive Antennas (PCAs) are amplified externally with an Erbium doped Fiber Amplifier (EDFA) module, which is being utilized for other nonlinear optical studies. The output of the laser-amplifier system is having a pulse repetition rate of 100 MHz, 70 fs and 380 mW of average power.
Time-resolved Spectroscopy using optical and THz radiation
An optical pump/THz probe technique called time-resolved THz spectroscopy (TRTS) is used to explore systems where a visual excitation triggers a change in the far-infrared absorption properties on a timescale of a few picoseconds. UPL is building TRTS system is built around an ultrafast Er-doped fiber laser at 1550 nm. Two beams are separated: one for the pump beam (connected to Optical Parametric Amplfiier) and the other for THz generation and detection. THz radiation is produced in a ZnTe(110) crystal using optical rectification, and it is detected in a second ZnTe(110) crystal through free-space electo-optic sampling. At the same spatial and temporal location as the pump beam, the THz beam is focussed onto the sample, to obtain various parameters regarding this study.
Development of high-energy Nd:YAG oscillator and amplifiers
