We have fabricated and characterized a n-doped InSb Faraday isolator in the mid-IR range (9.2 $mu$m). A high isolation ratio of $approx$30 dB with a transmission over 80% (polarizer losses not included) is obtained at room temperature. Further possible improvements are discussed. A similar design can be used to cover a wide wavelength range (lambda ~ 7.5-30 $mu$m).
Mid infrared (MIR) photonics is a key region for molecular physics [1]. High-resolution spectroscopy in the 1--10 {mu}m region, though, has never been fully tackled for the lack of widely-tunable and practical light sources. Indeed, all solutions pro
posed thus far suffer from at least one of three issues: they are feasible only in a narrow spectral range; the power available for spectroscopy is limited; the frequency accuracy is poor. Here, we present a setup for high-resolution spectroscopy that can be applied in the whole 1--10 {mu}m range by combining the power of quantum cascade lasers (QCLs) and the accuracy achievable by difference frequency generation using an OP-GaP crystal. The frequency is measured against a primary frequency standard using the Italian metrological fibre link network. We demonstrate the performance of the setup by measuring a vibrational transition in a highly-excited metastable state of CO around 6 {mu}m with 11 digits of precision, four orders of magnitude better than the value available in the literature [2].
Quantum information technologies harness the intrinsic nature of quantum theory to beat the limitations of the classical methods for information processing and communication. Recently, the application of quantum features to metrology has attracted mu
ch attention. Quantum optical coherence tomography (QOCT), which utilizes two-photon interference between entangled photon pairs, is a promising approach to overcome the problem with optical coherence tomography (OCT): As the resolution of OCT becomes higher, degradation of the resolution due to dispersion within the medium becomes more critical. Here we report on the realization of 0.54 $mu$m resolution two-photon interference, which surpasses the current record resolution 0.75 $mu$m of low-coherence interference for OCT. In addition, the resolution for QOCT showed almost no change against the dispersion of a 1 mm thickness of water inserted in the optical path, whereas the resolution for OCT dramatically degrades. For this experiment, a highly-efficient chirped quasi-phase-matched lithium tantalate device was developed using a novel $`$nano-electrode-poling$$ technique. The results presented here represent a breakthrough for the realization of quantum protocols, including QOCT, quantum clock synchronization, and more. Our work will open up possibilities for medical and biological applications.
Non-reciprocal photonic devices are essential components of classical optical information processing. It is interesting and important to investigate their feasibility in the quantum world. In this work, the quantum properties of an on-chip silicon ni
tride (SiN)-based magneto-optical (MO) isolator were studied using a single-photon non-reciprocal dynamical transmission experiment. The measured isolation ratio for single photons achieved was 12.33 dB, which proved the functionality of our on-chip isolator. The quantum coherence of the passing single photons was further verified using high-visibility quantum interference. Our work will promote on-chip isolators within the integrated quantum circuits and help introduce novel phenomena in quantum information processes.
We show that subwavelength silicon-rich nitride waveguides efficiently sustain high-speed transmissions at 2 $mu$m. We report the transmission of a 10 Gbit/s signal over 3.5 cm with negligible power penalty. Parametric conversion in the pulsed pump r
egime is also demonstrated using the same waveguide structure with an efficiency as high as -18 dB.
We report on higly accurate absolute frequency measurement against a femtosecond frequency comb of 6 saturated absorption lines of formic acid (HCOOH) with an accuracy of 1 kHz. We also report the frequency measurement of 17 other lines with an accur
acy of 2 kHz. Those lines are in quasi coincidence with the 9R(36) to 9R(42) CO$_2$ laser emission lines and are probed either by a CO$_2$ or a widely tunable quantum cascade laser phase locked to a master CO$_2$ laser. The relative stability of two HCOOH stabilized lasers is characterized by a relative Allan deviation of 4.5 10$^{-12}$ $tau^{-1/2}$. They give suitable frequency references for H$_2^+$ Doppler free two-photon spectroscopy.