Terahertz sideband-tuned quantum cascade laser radiation.

A compact, tunable, narrowband terahertz source was demonstrated by mixing a single longitudinal mode 2.408 THz, free running quantum cascade laser with a 2-20 GHz microwave sweeper in a conventional corner-cube-mounted Schottky diode. The sideband spectra were characterized with a Fourier transform spectrometer, and the radiation was tuned through several D(2)O rotational transitions to estimate the longer term (t > or = several sec) bandwidth of the source. A spectral resolution of 2 MHz in CW regime was observed.

3 µm CW lasers for myringotomy and microsurgery.

This paper describes the development and implementation of 3 µm lasers for myringotomy and microsurgery. Two different lasers were investigated. The first, an Er-doped, CW zirconate glass fiber laser optically pumped by a 970 nm diode laser, emitted > 1 W of CW power at 2.76 µm with concomitant green incoherent emission that served as a convenient visible illumination beam. The second, a 1 W CW Er:YAG solid-state laser also optically pumped by a 970 nm diode laser, emitted > 1 W of CW power at 2.94 µm, coincident with the strongest infrared water absorption peak. Running CW, both lasers are expected to avoid the loud acoustical shocks associated with pulsed lasers. Myringotomies were carried out with the Er:YAG laser on anaesthetized guinea pigs and the effects of the laser were documented. Laser ablated samples of tympanic membrane, soft tissue and bone were histologically examined. Histology results indicated that the CW Er:YAG laser is a potential candidate for a new myringotomy tool and possibly for otologic microsurgery, but deliverable power levels need to be increased to the 2 W (or higher) level. This work was funded under NIH SBIR Grant No. 5R44DC004899.

Transformation of the multimode terahertz quantum cascade laser beam into a Gaussian, using a hollow dielectric waveguide.

We demonstrate that a short hollow dielectric tube can act as a dielectric waveguide and transform the multimode, highly diverging terahertz quantum cascade laser beam into the lowest order dielectric waveguide hybrid mode, EH(11), which then couples efficiently to the free-space Gaussian mode, TEM(00). This simple approach should enable terahertz quantum cascade lasers to be employed in applications where a spatially coherent beam is required.