Mode-hop-free tunable high-power distributed feedback laser with adaptable rear facet phase shift section emitting at 780 nm.

We present a high-power ridge waveguide distributed feedback (DFB) laser with a high-reflective coating and a phase shift section at the rear facet. The phase shift section is realized by means of a micro heater that is placed parallel to the ridge waveguide and the uniform grating. This type of heater section is easy to integrate into existing laser designs and allows adjusting and controlling the spectral behavior of the distributed feedback laser by shifting the rear facet phase condition, which makes it possible to overcome the challenges of mode-hop-free tuning of regular DFB lasers with highly reflective cleaved rear facet. Accordingly, we use the device to quantify rear facet phase conditions where mode hops occur, which are compared to theory with good agreement.

Continuous-wave operation of DFB laser diodes based on GaN using 10$

Single longitudinal mode continuous-wave operation of distributed-feedback (DFB) laser diodes based on GaN is demonstrated using laterally coupled 10th-order surface Bragg gratings. The gratings consist of V-shaped grooves alongside a 1.5 µm wide p-contact stripe fabricated by using electron-beam lithography and plasma etching. By varying the period of the Bragg grating, the lasing wavelength could be adjusted between 404.8 and 408.5 nm. The feasibility of this device concept was confirmed by mode-hop-free operation up to an optical output power of 90 mW, a low temperature sensitivity of the lasing wavelength, and a Gaussian lateral far-field distribution.

Method for in-depth characterization of electro-optic phase modulators.

A flexible method to measure the modulation efficiency and residual amplitude modulation, including non-linearities, of phase modulators is presented. The method is based on demodulation of the modulated optical field in the optical domain by means of a heterodyne interferometer and subsequent analysis of the I&Q quadrature components of the corresponding RF beat note signal. As an example, we determine the phase modulation efficiency and residual amplitude modulation for both the TE and TM modes of a GaAs chip-based phase modulator at the wavelength of 1064 nm. From the results of these measurements, we estimate the linear and quadratic electro-optic coefficients for a P-p-n-N GaAs/AlGaAs double heterostructure.