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We present a Tm-doped fiber laser operating around 1.9 μm by bi-directional pumping with 1.6 μm-band laser diodes. The laser output pulse is built by using a gain-switching pump pulse with a bias pump pulse. The output pulse power is measured to 119 mW when the bias pump power and the gainswitching pulse power are 71.7 and 46.6 mW, respectively. The output power is changed by tuning the feedback ratio of the variable-ratio output coupler and maximized at the feedback ratio of 0.81. The laser wavelength varies from 1.88 to 1.92 μm depending on the length of the Tm-doped fiber.Laser output wavelength, μm Laser output wavelength against the length of the Tm-doped fiber

We present a low-threshold vertical-cavity dye laser that is pumped by an InGaN laser diode. This vertical-cavity laser has a 1.2-m-thick poly-N-vinylcarbazole active layer doped with coumarin 540A. The threshold pump power depended on the dye concentration and showed the minimum value of 16 mW/pulse with the dye concentration of 4.0%. Single-mode laser action is attained at around 550 nm and the output intensity decreases to half of the initial value after the emission of 8 ϫ 10 5 pulses. This concept helps to realize a highly compact dye laser that can be operated in the entire range of visible wavelengths.There has been considerable interest in organic lasers due to the variety of organic dyes and the flexibility of the device architectures. The broad lasing bands of these devices cover the midvisible wavelengths that cannot be realized by inorganic laser diodes ͑LDs͒. The current-injection mode of organic lasers is the most attractive technique for realizing compact organic lasers. On the other hand, considering the durability of dye molecules, optically pumped organic lasers have an advantage in that the active element is separated from the pumping element and, therefore, the former can be easily replaced. Thus far, various types of optically pumped organic lasers have been reported; 1-3 however, the pump sources for such lasers continue to be either the frequency doubled or tripled solid-state lasers or high-power gas lasers, which are expensive, bulky, and consume large amounts of power. In order to reduce the size and energy consumption of the lasers, the pump sources should be replaced with LDs. It is preferable to use violet and blue LDs to excite organic lasers that operate in the visible wavelength range. Recently, waveguide-type and vertical-cavity-type polymeric dye lasers were oscillated using InGaN LDs, which required a threshold pump power of more than 100 mW. 4,5 We intend to reduce the pump power required for laser operation to the milliwatt level in order to extend the lifetime of the organic dyes and enable the realization of diode-pumped polymeric dye lasers with low power consumption. In this letter, we report a reduction of the pump LD power that is required for lasing on the basis of a vertical cavity structure.The diode-pumped polymeric dye laser comprises a pump LD, collimator and focusing lens, and dye laser element ͑DLE͒, as shown in Fig. 1. The focusing optics of this laser can be ignored when the DLE is packaged with the pump LD. We used the InGaN-based blue LD ͑Nichia͒ as a pump source; the light emitted by this source had a wavelength of 441 nm. We operated the blue LD with a pulsedcurrent circuit that utilized an avalanche transistor to produce an optical pulse with a duration of ϳ3 ns. The DLE is comprised of a polymeric active layer that is sandwiched between two ͑top and bottom͒ distributed Bragg reflectors ͑DBRs͒. Such a vertical-cavity laser structure has a large aperture to accept the output light of the pump LDs and it can be arranged in two-dimensional configurations. We ...

Optically pumped organic thin-film lasers were fabricated by stacking top and bottom Bragg reflectors with an inner-cavity active layer between the reflectors. We observed single-longitudinal-mode laser operation at 555 nm by doping pyrromethene-567 dye into all the stacked layers. The threshold of the laser was 30% less than that of a laser operated with nondoped Bragg reflectors, which was in good agreement with calculations.