Although the field of gas phase rotational spectroscopy is mature and millions of rotational spectral lines have been measured in hundreds of molecules with sub-MHz accuracy, it remains a challenge to measure these rotational spectra in excited vibrational modes with the same accuracy. Based on the recently demonstrated quantum cascade laser (QCL) pumped molecular laser (QPML) we demonstrate how an infrared QCL may be used to enhance absorption strength or induce lasing of terahertz rotational transitions in highly excited vibrational modes in order to measure their frequencies more...

Ph.D. candidate  Joon-Suh Park has been selected as a top DARPA Riser and has presented his work on mass-producible, 10-centimeter diameter metalenses in the visible at the recent DARPA Forward conference. The 10 cm metalens is the largest ever fabricated in history, with 18.7 billion subwavelength nanostructures made of glass. 

From DARPA: DARPA...

Electro-optic modulators change the intensity of light in response to electric signals and have attracted much attention recently as they enable active photonics. Reaching gigahertz speeds is an important milestone that makes applications in remote sensing and communications accessible. Most demonstrations target either on-chip or fiber applications. Instead, modulators that operate on free-space light have long been very challenging to realize. Here, we show that a thin film metasurface from sub-wavelength Mie resonators enables highly efficient and ultra-compact modulation of light up...

Current achromatic metalenses are typically small and bounded to tens to hundreds of micrometers in diameter – the size of a few pollen grains in a row. In this study, we demonstrate a high throughput inverse design framework that is able to design large-scale complex metasurfaces to the cm scale for the visible, which corresponds to 20 000 times the wavelengths. The inverse design framework takes advantage of machine intelligence instead of our physical intuition, and the whole process takes less than a day using a single-CPU laptop, making it accessible to the general public. The...

In recent work, we have shown that a suitably-designed polarization-sensitive metasurface grating when paired with a conventional imaging system can serve as an "attachment" rendering it capable of polarization imaging. We describe the design rules that govern this process, and show as an example the adaptation of a simple machine vision camera with a metasurface grating.

More broadly, the work serves as a guide to using metasurface polarization gratings in optical systems more generally. These may be used as a polarization-sensitive component in a wide variety of contexts,...

Terahertz radiation lies in the transition region between the microwave and infrared spectra. It has much potential in civil and defence applications, including communications, imaging, and spectroscopy. Yet, the major obstacle to the widespread use of this spectrum has...