Anish K. Goyal of Block Engineering/MEMS,

The detection and identification of trace chemicals on surfaces is of great interest for a variety of civilian
and security applications. Sensitive techniques for trace surface detection already exist, but these
usually require the physical transfer of chemicals from the surface of interest into the instrument. In
some cases, however, it is desirable that detection occur in a standoff configuration and be non-
destructive. Furthermore, it is often desirable to rapidly scan the surface and to map the chemical
contamination with high spatial resolution.
Laser-based, long-wave infrared (LWIR) hyperspectral imaging has been shown to be capable of
addressing many of the requirements that are important to end users. These include the ability to
engineer hand-portable systems that are eye-safe (class 1), provide high sensitivity detection
(micrograms/cm 2 ), operate at modest standoff distances (<1m to >10m), and achieve high areal
coverage rates (potentially >100 cm 2 /s).

Wavelength-tunable quantum-cascade lasers (operating wavelength about = 7.5 – 12 um) are used to illuminate
the surface of interest and a camera captures the diffusely reflected light. The laser wavelength is tuned
synchronously with the camera such that reflectance of the surface in the form of a hyperspectral image
cube (hypercube) in which each pixel represents the reflection spectrum of a single point on the surface.
The unique spectral signature of chemicals can be detected with high sensitivity because of the very
large absorption cross-sections for most chemicals in the LWIR.

Over the past 15 years, this technology has matured from initial feasibility demonstration (at MIT/LL)
and then through the development of a series of prototypes under funding from IARPA, DoD, and DHS.
It is currently on the cusp of being commercialized. In this talk, we will discuss the underlying
technology, performance limits, and present examples of various applications.

Biography:

Anish Goyal is the Vice President of Technology at Block Engineering. Responsibilities include the
advancing of Block’s chemical detection products and the external-cavity quantum cascade lasers on
which these products are based. Prior to joining Block, he was a member of the Technical Staff at MIT
Lincoln Laboratory in the Laser Technology and Applications Group. His academic background is in
Electrical Engineering, receiving a B.S. degree from Rensselaer Polytechnic Institute and Ph.D. from the
University of California, Santa Barbara.