CC BY
0The 30th International Conference on Advanced Laser Technologies
N-I-10
ALT'23
Effect of magnetic field and injection current on spectral characteristics of multiple quantum well laser
Aurangzeb Khurram Hafiz
Centre for Nanoscience and Nanotechnology, Jamia Millia Islamia, New Delhi - 110025, INDIA
ahafiz@jmi.ac. in
The spectral characteristics of MQW Laser is extremely sensitive to the presence of magnetic field as well as injection current density. The study on the effect of drive current on the spectral emission of the laser device in absence of magnetic field (B = 0Tesla) typically results in the variation of the peak frequency of the spectrum as the drive current is increased from threshold and above. As the drive current increases, the number of longitudinal modes that are present, may compete with each other in the gain medium. This results in narrower spectral width and the average mode gain decreases. According to our laser model, the central mode (lasing mode) grows faster than the adjacent modes at current near threshold, and eventually the amplitudes of the adjacent modes effectively saturate. At a particular output level, additional increase in power is due to growth of a single primary mode. The output of the laser diode is shifted by two primary effects, current induced changes in the junction temperature, and charge carrier induced refractive index changes. Thermally induced changes are a result of thermal expansion of Fabry-Perot laser cavity and changes in the refractive index, which combine to increase the output wavelength with increasing junction current. As the single-mode power increases, a standard wave arises in the laser cavity. Carriers are depleted faster at the peaks of the standard wave than in the surrounding areas, which results in decrease in the average mode gain. This effect is known as 'spatial hole burning'. The depleted carriers have to be replenished by carrier diffusing into these regions. Thus, the amount of gain suppression of the lasing mode depends upon the diffusion rates of electrons and holes.
In presence of magnetic field, the response of the charge carriers in the active region is guided by the Hall effect dynamics. Several decades ago, the dynamics of the charge carriers in double-heterostructure (DH) lasers was studied under the condition of high magnetic field (about 10T) and very low temperature (T<<100k) [1-2]. In the condition of strong magnetic field and very low temperature, a blue-shift in the DH laser spectral characteristics was observed. This was explained well with Landau level-based theory. The necessary condition for the formation of Landau levels is (kT << h&C) where (rac) is the angular frequency of the cyclotron orbit. This condition is only achieved at very low temperature (T<<100K) and strong magnetic fields.
Around the room temperature, the thermal agitation is high enough to wash out Landau splitting. Also, contrary to the observed higher frequency side shifts of the oscillation wavelength of semiconductor lasers at low temperature and high magnetic fields, researcher have obtained shifts in the oscillating wavelength toward the lower frequency side, indicating device heating effects. In order to explain the observed effects at room temperature and low magnetic fields, researchers have propounded theory based on the heating of the active region of the device and longitudinal magneto-resistance effect [3-4].
In this work an attempt is made to correlate the charge carrier dynamics of MQW laser system under the following two conditions:
a) Strong magnetic field (> 5T) and very low temperature (T<<100K).
b) Low magnetic field (< 2T) and room temperature (280K-300K) condition.
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[2] Arakawa, y., Sakaki, H., Nishioka, M., Okamoto, M.m and Miura, N., Spontaneous emission characteristics of quantum well lasers in strong magnetic fields - an approach to quantum-well-box light source, Jpn. J. Appl. Phys., 22, L804-L806 (1983).
[3] Sato, T., Magnetic field effect on oscillation characteristics of a semiconductor laser, Rev. of Laser Engineering, 22, 91-99 (1994).
[4] Zaker, T. A., and Hafiz, A. K., Influence of Magnetic field on threshold current, temperature characteristics,and on the output power in AlGalnP Multiple Quantum well Laser, Appl. Phys. Res., 3, 143-151 (2011).
