Narrow-linewidth quantum cascade laser at 8.6 μm.

We report on a narrow-linewidth distributed-feedback quantum cascade laser at 8.6 μm that is optical-feedback locked to a high-finesse V-shaped cavity. The spectral purity of the quantum cascade laser is fully characterized using a high-sensitivity optical frequency discriminator, leading to a 1 ms linewidth of less than 4 kHz and a minimum laser frequency noise spectral density as low as 0.

mα(7)-order corrections in the hydrogen molecular ions and antiprotonic helium.

We present a calculation of the complete set of QED corrections of order mα7 for one-electron two-center systems. Leading corrections of order mα8 are also considered, which allows us to estimate the magnitude of yet uncalculated contributions. The theoretical uncertainty on the frequencies of rovibrational transitions in the hydrogen molecular ions H2+ and HD+, and of two-photon transition in antiprotonic helium is reduced by about 1 order of magnitude, down to (3-4)×10-11 and 10-10, respectively.

Why three-body physics does not solve the proton-radius puzzle.

The possible involvement of weakly bound three-body systems in the muonic hydrogen spectroscopy experiment, which could resolve the current discrepancy between determinations of the proton radius, is investigated. Using variational calculations with complex coordinate rotation, we show that in the pμe ion, which was recently proposed as a possible candidate, the pμ core fails to bind the outer electron tightly enough to explain the discrepancy. It is also shown that the ppμ molecular ion cannot play any role in the observed line.

Note: a high transmission Faraday optical isolator in the 9.2 μm range.

We have fabricated and characterized an n-doped InSb Faraday isolator in the mid-IR range (9.2 μm). A high isolation ratio (31(2) dB) and low insertion loss (1.

Frequency doubling of CO2 laser radiation at 10.6 microm in the highly nonlinear chalcopyrite LiGaTe2.

Type-I phase matching for second-harmonic generation at 10.6 microm in LiGaTe(2) is demonstrated by using a tunable single-frequency continuous-wave CO(2) laser, and the nonlinear coefficient of LiGaTe(2) is determined from comparison with AgGaSe(2). The effective nonlinearity of LiGaTe(2) for this process amounts to 34.

Narrow-line phase-locked quantum cascade laser in the 9.2 microm range.

We report the operation of a 50 mW continuous-wave quantum cascade laser (QCL) in the 9.2 microm range, phase locked to a single-mode CO(2) laser with a tunable frequency offset. The wide free-running emission spectrum of the QCL (3-5 MHz) is strongly narrowed down to the kilohertz range, making it suitable for high-resolution molecular spectroscopy.