Masao Majima

Polarization switching in AlGaAs/GaAs distributed feedback lasers between the stable single longitudinal modes

TE/TM polarization mode switching is demonstrated in an AlGaAs/GaAs distributed feedback laser diode. The device has two current injecting electrodes and as an active layer a conventional multiquantum well (MQW) structure. A small amplitude modulation of the current into one of the electrodes switches the polarization mode. Each mode corresponds to a stable single longitudinal mode of a distributed feedback laser. The lasing wavelength can be tuned continuously, without mode hopping, over 0.7 nm by controlling the total injection current. This new kind of polarization switching is promising for optical switching systems and optical frequency division multiplexing devices.

Polarization switching in a tensile-strained InGaAs/InGaAsP multiple quantum well distributed feedback laser diode

An inhomogeneously biased distributed feedback (DFB) laser diode (LD) with two electrodes switched its polarization mode by 3 mA change of the bias current, maintaining single longitudinal mode oscillation. In the active layer of the LD, 13 nm thick and 0.6% tensile-strained InGaAs multiple quantum well (MQW) equalized the transverse electric and the transverse magnetic modal optical gain at 1.55 μm. With various grating pitches on the same MQW active layer, polarization switching DFB LDs were realized in the wavelength range as wide as 18 nm. The linewidth characteristics during the polarization switching were confirmed to be narrow due to the small switching current.