A wide range of laser medical treatments are based on coagulation of blood by absorption of the laser radiation. It has, therefore, always been a goal of these treatments to maximize the ratio of absorption in the blood to that in the surrounding tissue. For this purpose lasers at 577 nm are ideal since this wavelength is at the peak of the absorption in oxygenated hemoglobin. Furthermore, 577 nm has a lower absorption in melanin when compared to green wavelengths (515 − 532 nm), giving it an advantage when treating at greater penetration depth. Here we present a laser system based on frequency doubling of an 1154 nm Distributed Bragg Reflector (DBR) tapered diode laser, emitting 1.1 W of single frequency and diffraction limited yellow light at 577 nm, corresponding to a conversion efficiency of 30.5%. The frequency doubling is performed in a single pass configuration using a cascade of two bulk non-linear crystals. The system is power stabilized over 10 hours with a standard deviation of 0.13% and the relative intensity noise is measured to be 0.064 % rms.
Optically pumped polymer photonic crystal band-edge dye lasers are presented. The photonic crystal is a rectangular
lattice providing laser feedback as well as an optical resonance for the pump light. The lasers are defined in a thin film of
photodefinable Ormocore hybrid polymer, doped with the laser dye Pyrromethene 597. A compact frequency doubled
Nd:YAG laser (352 nm, 5 ns pulses) is used to pump the lasers from above the chip. The laser devices are 450 nm thick
slab waveguides with a rectangular lattice of 100 nm deep air holes imprinted into the surface. The 2-dimensional
rectangular lattice is described by two orthogonal unit vectors of length a and b, defining the ΓP and ΓX directions. The
frequency of the laser can be tuned via the lattice constant a (187 nm - 215 nm) while pump light is resonantly coupled
into the laser from an angle (θ) depending on the lattice constant b (355 nm). The lasers are fabricated in parallel on a 10
cm diameter wafer by combined nanoimprint and photolithography (CNP). CNP relies on a UV transparent quartz
nanoimprint stamp with an integrated metal shadow mask. In the CNP process the photonic crystal is formed by
mechanical deformation (imprinting) while the larger features are defined by UV exposure through the combined
mask/mold.
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