optics setup
Ultrafast Spectroscopy
Ultrafast spectroscopy uses extremely short laser pulses to observe processes that occur on femtosecond (10⁻¹⁵ s) time scales. These techniques allow researchers to directly measure how excited electronic states evolve in materials immediately after optical excitation. Because many fundamental processes in semiconductors, such as carrier scattering, recombination, and energy relaxation, occur on femtosecond to picosecond time scales, ultrafast spectroscopy provides a powerful tool for understanding the physics that governs modern optoelectronic devices.
In our laboratory we use ultrafast pump-probe spectroscopy, in which a short “pump” pulse excites carriers in a semiconductor and a delayed “probe” pulse measures the resulting changes in optical transmission or reflectivity. By varying the delay between the pulses, we can reconstruct how carriers relax, recombine, and interact with phonons and defects inside the material.
Our ultrafast measurements are used to study carrier dynamics in a variety of semiconductor nanostructures, including superlattices, nanowires, and quantum-confined heterostructures used for infrared optoelectronic devices. These experiments provide insight into processes such as:
- Carrier lifetimes and recombination mechanisms
- Carrier transport and diffusion
- Energy relaxation through phonon scattering
- Optical nonlinearities and light–matter coupling
Understanding these processes helps guide the design of improved semiconductor materials and device architectures for infrared emitters, detectors, and nanophotonic systems.
By combining ultrafast optical measurements with materials growth and nanofabrication, our group connects fundamental carrier dynamics with the performance of real photonic devices, enabling more efficient and scalable semiconductor technologies.