Quantum cascade lasers (QCLs), increasingly used for medical spectroscopy diagnostics, operate using a pulsed technique across a broad range of wavelengths. Yokogawa's OSA AQ6377 performs stable measurements across this wide wavelength range and is also capable of evaluating pulsed QCL signals with low repetition rates. The AQ6377 thus represents a significant advancement, enabling researchers to work with various pulse lengths and repetition rates.
The AQ6377's key features include a wavelength resolution of 0.2 nm, wavelength accuracy of ±0.5 nm, a high dynamic range of 50 dB, and a sensitivity level below -60 dBm. The dynamic range and high sensitivity are achieved by minimizing the influence of stray light on the monochromator. The built-in calibration light source utilizes the natural absorption properties of acetylene gas to emit a wavelength calibration signal accurate to 0.6 picometers. This source is also used in conjunction with the automatic optical alignment capability to compensate for any optical axis deviation caused by vibrations during transport and temperature changes.
Furthermore, the clear-space optical entry allows both single-mode and multimode MWIR fibers (up to 400 µm) to be connected to the same device, offering low and stable insertion loss, which increases measurement repeatability. The absence of physical contact eliminates the possibility of damaging the fibers during connection.
Another important feature of the AQ6377 is purging. In the MWIR region, spectral measurements can be influenced by the absorption of water vapor and carbon dioxide. The purging function is designed to reduce the influence of these gases by supplying a pure purge gas, such as nitrogen, to the monochromator via dedicated connectors located on the rear panel.
