Single- and Dual-Frequency Laser Diodes based on Surface Gratings
Research output: Book/Report › Doctoral thesis › Collection of Articles
|Publisher||Tampere University of Technology|
|Number of pages||80|
|Publication status||Published - 3 Aug 2018|
|Publication type||G5 Doctoral dissertation (article)|
|Name||Tampere University of Technology. Publication|
Laterally-coupled ridge-waveguide (LC-RWG) surface gratings with alternating lateral protrusions were developed to circumvent the etching aspect ratio limitation that prevents the fabrication of low-order short-wavelength surface gratings. The single longitudinal mode DFB lasers with alternating LC-RWG gratings emitting around 780 nm demonstrated improved performances, particularly important for the space borne target applications.
The dual longitudinal mode emission was achieved by periodically placing phase shifts along the grating. The experiments showed that the direct amplitude modulation bandwidth is extended when the photon-photon resonance associated with dual-mode emission is properly placed with respect to the carrier-photon resonance and when both resonances are adequately damped. Diﬀerence frequency range controlled by structural variations and 40 GHz diﬀerence frequency tuning by bias were demonstrated, as well as high speed diﬀerence frequency modulation. Linearly apodized LC-RWG surface gratings enabled a lower threshold current, a higher output power, and a broader range of diﬀerence frequency tunability by bias. Also the apodization and the complex-coupling of the surface gratings enabled the use of higher facet reﬂectivities, leading to narrower intrinsic short timescale linewidths. The achieved performance improvements indicate that the studied laser types are promising solutions for their target applications.