We demonstrate the full frequency stabilization of a Quantum Cascade Laser Frequency Comb by using radio-frequency injection for locking the mode spacing and frequency locking to a crystalline microresonator for stabilizing the offset frequency. A final mode linewidth of 30 kHz over 2 ms is achieved.
Interband Cascade Lasers are becoming more and more attractive sources for sensing applications due to their direct mid-IR emission and low power consumption. In many demanding applications of precision spectroscopy and imaging, the laser frequency and intensity noise represent the ultimate limiting factor for the final sensitivity. Here, we first characterize the response of a DFB ICL to a frequency modulation and measure its tuning coefficients. A frequency noise analysis of the ICL is then provided, through experimental investigation of the frequency noise power spectral density, with a particular attention to the technical noise contribution. A possible scheme for frequency stabilization and linewidth narrowing is presented through frequency locking to a high-Q factor microresonator.
The use of light for sterilization is very well known in the scientific literature. However, the recent pandemic outbreak and the antimicrobial resistance question drew attention to this topic: to design new light sources for preventing viral epidemic spread is of utmost importance, as an alternative use of chemicals and drugs. Here we present the preliminary ex vivo studies aiming at verifying the potential of new UVC light sources as barriers to the spread of airborne viruses and bacteria. The emitted light is at very short wavelengths (around 220 nm): optical penetration in biological media is limited to a few micrometers, thus preventing the possible damages to the skin and the cornea; the absorption of RNA/DNA shows a minimum at 230 nm, increasing at shorter wavelengths. In this study we optimized a UVC commercial excimer lamp to design a light barrier. The sterilization efficacy has been tested in vitro in cultured Staphylococcus aureus, Pseudomonas aeruginosa and in Sars-Cov-2. The results point out a strong antimicrobial effect (<99.9% bacteria reduced) at ∼15 mJ/cm2 (corresponding to 1 minute treatment time @0.25 mW/cm2). The designed prototype can thus be proposed as a light barrier for preventing contamination, reducing the risks for human beings.
Interband Cascade Lasers (ICLs) are gaining field in molecular sensing thanks to their compact sizes and low-power consumption. They emit in the 3-6 μm range, and are valid alternative to QCLs especially for on-field measurement. Their suitability for high-resolution spectroscopy and metrology critically depends on their frequency stability and linewidth.
Here we investigate this issues, reporting experimental studies of the frequency noise and intrinsic linewidth of an ICL at 4.6 μm. The main differences with respect to other semiconductor lasers are discussed, as well as quantum-limited operation achievable using low-noise current drivers and frequency locking to high-performance optical resonators.
Interband and Quantum Cascade Lasers are key sources for MIR molecular sensing. Understanding their noise features and stabilizing their emission is of fundamental importance for applications like precision spectroscopy and metrology. High-Q crystalline Whispering Gallery Mode Resonators have proven to be powerful tools for characterization and stabilization of lasers from the UV to the MIR. Here, we report our recent results on Whispering Gallery Mode Resonators used for frequency characterization, stabilization and linewidth narrowing of Interband and Quantum Cascade Lasers. These results pave the way to new classes of compact MIR sources usable in Space missions, Metrology and Fundamental Physics.
We report on a metrological-grade mid-IR source with a 10–14 short-term instability for high-precision spectroscopy. Our source is based on the combination of a quantum cascade laser and a coherent radiation obtained by difference-frequency generation in an orientation-patterned gallium phosphide (OP-GaP) crystal. The pump and signal lasers are locked to an optical frequency comb referenced to the primary frequency standard via an optical fiber link. We demonstrate the robustness of the apparatus by measuring a vibrational transition around 6 μm on a metastable state of CO molecuels with 11 digits of precision.
Orientation-patterned gallium phosphide (OP-GaP) crystals are used here for the first time for the generation of continuous-wave coherent mid-infrared radiation around 5.85 μm by difference frequency generation (DFG) of a Nd:YAG laser at 1064 nm and a diode-laser at 1301 nm. We provide the first characterization of the linear, thermo-optic and nonlinear properties of OP-GaP in a DFG configuration, and we derive an effective nonlinear coefficient deff = 17 pm/V (3) for first-order quasi-phase-matched OP-GaP. This novel nonlinear material can be used to referenced the mid-IR light to a frequency standard by locking the pump and signal laser to a near-IR optical frequency comb.
Narrow-linewidth lasers are key elements in optical metrology and spectroscopy. From their spectral purity, the measurements accuracy and the overall quality of collected data critically depend. Crystalline micro-resonators have undergone an impressive development in the last decade, opening new ways to photonics from the mm to the μm scale. Their wide transparency range and high Q-factor make them suitable for integration in compact apparatuses for precision spectroscopy from the visible to the mid-IR. Here, we present our recent results on frequency stabilization and linewidth narrowing of quantum cascade lasers using crystalline Whispering Gallery Mode Resonators for mid-IR precision spectroscopy.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.