Abstract
Molecules such as water, proteins and lipids that are contained in biological tissue absorb mid-infrared (MIR) light, which allows such light to be used in laser surgical treatment. Esters, amides and water exhibit strong absorption bands in the 5–7 μm wavelength range, but at present there are no lasers in clinical use that can emit in this range. Therefore, the present study focused on the quantum cascade laser (QCL), which is a new type of semiconductor laser that can emit at MIR wavelengths and has recently achieved high output power. A high-power QCL with a peak wavelength of 5.7 μm was evaluated for use as a laser scalpel for ablating biological soft tissue. The interaction of the laser beam with chicken breast tissue was compared to a conventional CO 2 laser, based on surface and cross-sectional images. The QCL was found to have sufficient power to ablate soft tissue, and its coagulation, carbonization and ablation effects were similar to those for the CO 2 laser. The QCL also induced comparable photothermal effects because it acted as a pseudo-continuous wave laser due to its low peak power. A QCL can therefore be used as an effective laser scalpel, and also offers the possibility of less invasive treatment by targeting specific absorption bands in the MIR region.
Highlights
In 1994, Faist et al succeeded in fabricating a quantum cascade lasersQuantum cascade lasers (QCLs) with a peak emission wavelength of 4.3 m based on intersub-band transitions in an InGaAs/InAlAs multiple quantum well and superlattice structure.[2]
The present study focused on the QCL, since it is a compact semiconductor-based laser, it has recently become capable of high output power, and it can be made to emit in the desired wavelength range of 5–7 m
E®ects of QCL irradiation on chicken breast tissue. (a) Surface view and (b) cross-sectional view
Summary
Quantum cascade lasers (QCLs) are a new type of semiconductor laser that utilize sub-band transitions in semiconductor multilayer structures. Light emission from a QCL occurs by transitions between sub-bands formed in an articially designed semiconductor multilayer structure (quantum cascade). It is possible to tune the emission wavelength over a wide range because it is determined primarily by the thickness of the individual layers.[1] In 1994, Faist et al succeeded in fabricating a QCL with a peak emission wavelength of 4.3 m based on intersub-band transitions in an InGaAs/InAlAs multiple quantum well and superlattice structure.[2] In 2001, continuous wave (CW) room-temperature emission at mid-infrared (MIR) wavelengths was reported,[3] followed by terahertz emission in 2002.4 QCLs are capable of emission at both mid- and far-infrared wavelengths
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