400  mW external cavity diode laser with narrowband emission at 445  nm

Abstract

A high-power external cavity diode laser (ECDL) system with narrowband emission is presented. The system is based on a commercially available high-power GaN laser diode. For the ECDL, a maximum optical output power of 400 mW in continuous-wave operation with narrowband emission is achieved. Longitudinal mode selection is realized by using a surface diffraction grating in Littrow configuration. A spectral width of 20 pm at 445 nm with a side-mode suppression ratio larger than 40 dB is achieved. This concept enables diode laser systems suitable for subsequent nonlinear frequency conversion into the UV spectral range.

Single-pass UV generation at 2225 nm based on high-power GaN external cavity diode laser

“…The deviation in the conversion coefficient by a factor of 3.6 as well as the larger beam waist radius in our experiment is probably due to the nondiffraction limited fundamental beam of the ECDL. As reported in [13], the second moment beam propagation factors for the ECDL emission at 400 mW are M 2 lat:;4σ 8.2 and M 2 vert:;4σ 4.9 in the lateral and vertical direction, respectively. Figure 3 also shows an increasing deviation of the experimental data points from the numerical fit for higher pump powers.…”

“…However, their broad spectral emission limits their applicability for frequency conversion. In order to reduce the spectral width, a high-power GaN laser diode in an external cavity diode laser (ECDL) system in Littrow configuration was recently presented by the authors [13].…”

“…First, the lowest diffraction efficiency of the grating of 15% in p-plane can be used. This proved to be appropriate to spectrally stabilize the laser diode and assures that as much as 80% of the incident power on the grating can be coupled out by the 0th order reflection [13]. Second, the polarization is correctly aligned for type-I phase-matching applied here.…”

“…Figure 3 also shows an increasing deviation of the experimental data points from the numerical fit for higher pump powers. This might be due to the increase of the spectral width of the ECDL emission for output powers beyond 400 mW [13]. Figure 4 shows a spectrum of the generated secondharmonic emission at λ 222.5 nm and the residual stray light from the fundamental at 445 nm at a pump power of 400 mW.…”

Tuning range and output power optimization of an external-cavity GaN diode laser at 455 nm

“…Another 405 nm external-cavity diode laser was demonstrated by Lv et al in 2013, with an output power of the laser around 1 mW and with a tuning range around 4.5 nm [12]. Recently, Ruhnke et al reported an external-cavity diode laser at 445 nm, where a maximum output power of 400 mW was obtained, and the tuning range was around 3 nm [13]. This externalcavity diode laser system was used as a pump source to generate deep violet radiation at 222.5 nm [5].…”