The Tiny Laser Is An Important Step Toward New Sensors

A study developing towards portable scanners; that can rapidly measure molecules in pharmaceuticals or classify tissue in patients’ skin; researchers have creating an imaging system that using lasers small and efficient enough to fit on a microchip sensors. The system emits and detects electromagnetic radiation at terahertz frequencies higher; than radio waves but lower than the long-wave infrared light used for thermal imaging.

Imaging using terahertz radiation has long been a goal for engineers, but the difficulty of creating practical systems that work in this frequency range has stymied most applications and resulted in what engineers call the terahertz gap. A revolutionary technology that does not have any moving parts and uses direct emission of terahertz radiation from semiconductor chips.

Step toward new sensors

Terahertz radiation can penetrate substances such as fabrics and plastics, is non-ionizing and therefore safe for medical use, and can be used to view materials difficult to image at other frequencies. The device uses stable beams of radiation at precise frequencies. The setup is called a frequency comb because it contains multiple “teeth” that each emit a different, well-defined frequency of radiation.

The radiation interacts with molecules in the sample material. A dual-comb structure allows the instrument to efficiently measure the reflected radiation. Unique patterns, or spectral signatures, in the reflected radiation allow researchers to identify the molecular makeup of the sample. While current terahertz imaging technologies are expensive to produce and cumbersome to operate; the new system is based on a semiconductor design that costs less and can generate many images per second.

Terahertz imaging system

This speed could make it useful for real-time quality control of pharmaceutical tablets on a production line and other fast-paced uses. Imagine that every 100 microseconds a tablet is passing by; and you can check if it has a consistent structure and there’s enough of every ingredient you expect. The terahertz imaging system identified each ingredient and revealed the boundaries between them, as well as a few spots where one chemical had spilled over into a different zone.

This type of “hot spot” representing a frequent problem in pharmaceutical production; that occuring when the active ingredient is not properly mixing into a tablet. While the technology makes the industrial and medical use of terahertz imaging more feasible than before; it still requires cooling to a low temperature, a major hurdle for practical applications. Because it is non-ionizing, terahertz radiation is safe for patients; and could potentially be using as a diagnostic tool for skin cancer.