TOPO

Mid-infrared tunable lasers between 2 – 5 µm are necessary tools for applications like high resolution molecular spectroscopy and gas sensing, mid-infrared integrated photonics, optical component characterization, and quantum optics. For this reason, TOPTICA has developed a continuous wave optical parametric oscillator that delivers the widest coverage of any MIR laser in this wavelength range. This system, the TOPO, has high power and narrow linewidth, and is capable of fast phase and frequency modulation necessary for sensitive gas phase MIR spectroscopy techniques.

The TOPO fills a critical gap in existing continuous wave laser technology. TOPTICA offers various tunable diode laser platforms to provide wide wavelength coverage below 2 µm. Wavelengths longer than 4 µm can be generated by quantum cascade lasers. Interband cascade lasers are the only laser diode technology with direct emission between 2 – 4 µm, and these lasers tend to have very small tuning ranges (few nm) and low output power (1 mW). The TOPO relies on TOPTICA’s long experience with efficient nonlinear frequency conversion of diode lasers to generate a high power MIR laser with wide tuning range.

The 2 – 5 µm range (5000 – 2000 cm^-1) is of interest for MIR spectroscopy because molecular stretch vibrations tend to have absorption features here. The TOPO is an ideal tool for direct tunable laser absorption spectroscopy of such molecular features. Direct TDLAS has limited sensitivity, detecting absorption coefficients α down to approximately 10^-4 per cm. More sensitive techniques require manipulation of the laser source. Fast frequency modulation is required for frequency modulation spectroscopy (minimum detectable α ~ 10^-6 cm^-1) and laser frequency stabilization is required for cavity-enhanced spectroscopy (minimum detectable α ~ 10^-8 cm^-1) and cavity ring-down spectroscopy (minimum detectable α < 10^-10 cm^-1). TOPTICA’s laser modulation and stabilization electronics, developed for quantum technology applications, transfer seamlessly to the TOPO for these sensitive absorption spectroscopy techniques.

Of course, the TOPO is useful not only for MIR spectroscopy, but also in any case where a mid-IR laser is required. On-chip MIR photonic devices are used for gas and biological sensing, and the TOPO is a useful tool for MIR integrated photonic characterization. Quantum memories generate single photons at wavelengths corresponding to transitions in atoms, quantum dots, and vacancy centers, and these wavelengths are often unsuitable for long distance propagation in optical fibers. Nonlinear frequency conversion of single photons to telecom wavelengths requires high power in a narrow spectrum at a strange wavelength, and the TOPO excels at providing exactly this kind of light. And undoubtedly there are other applications for the TOPO waiting to be found, please submit a request for more information and TOPTICA will be glad to work with you!

Characteristic Tuning Curve