Abstract
A reliable and power-scalable extended cavity diode-pumped passively mode-locked Yb:KGW laser generating ~200 fs long pulses at a repetition rate of 15 MHz was developed and characterized. The laser delivered up to 150 mW of average power at fundamental wavelength of 1040 nm, corresponding to a pulse energy of 10 nJ. The laser radiation was frequency-doubled in a single pass configuration within a nonlinear BIBO crystal to produce femtosecond green radiation at 520 nm with peak power of ~200 W. The generated second harmonic served as excitation source for optical DNA biosensor based on fluorescence lifetime measurements obtained using the time-correlated single photon counting technique.
Highlights
Optical DNA sensor technology has many potential applications in medicine, environmental monitoring, and pathogen detection, if the sensor device is capable of offering high detection selectivity, sensitivity in addition to reusability and the ability to provide for real-time monitoring [1, 2]
In this paper we report on the design and application of a diode-pumped femtosecond extended cavity Yb:KGW laser, which was subsequently frequency-doubled and used as a source for optical DNA sensing
It is required that the laser source should provide a pulse repetition rate corresponding to a period of at least 60 ns to permit for investigation of the long-lifetime component of ethidium bromide intercalated into doublestranded nucleic acid structures (~20 ns) [3]
Summary
Optical DNA sensor technology has many potential applications in medicine, environmental monitoring, and pathogen detection, if the sensor device is capable of offering high detection selectivity, sensitivity in addition to reusability and the ability to provide for real-time monitoring [1, 2]. The main points which determined these features of our laser system came form the following considerations: the use of a Yb:KGW crystal [15] as a laser gain medium instead of, for example, Nd:YAG or Nd:YVO4, as the Nddoped crystalline hosts exhibit narrow gain bandwidths and only supports the generation of picosecond pulses [4], reducing temporal resolution Such lasers usually rely on the use of expensive high-power (> 15-25 W) fiber-coupled laser diode modules. The crystal of Yb:KGW has a lower quantum defect, lower pump saturation intensity, and higher stimulated emission cross section when compared to other quasi-three-level Yb-doped laser materials, such as Yb:YAG: all contributing to the increased laser efficiency [17,18,19,20,21] It is worth mentioning, that to the best of our knowledge, low repetition rate operation of a femtosecond Yb:KGW laser pumped by multimode telecom-grade laser diodes has not been reported. Using high-power diode modules (> 20 W) a 10 MHz operation of an Yb:KGW laser system was demonstrated by Amplitude Systemes [22]
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