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Enhanced 1524-nm Emission From Ge Quantum Dots in a Modified Photonic Crystal L3 Cavity

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10 Author(s)
Yong Zhang$^{1}$ Wuhan National Laboratory for Optoelectronics, School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan, China ; Cheng Zeng ; Danping Li ; Zengzhi Huang
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Light emitters based on Ge quantum dots embedded in modified photonic crystal three defect-long (L3) cavities are fabricated and characterized. Several sharp resonant luminescence peaks dominate the photoluminescence (PL) spectrum at room temperature. The strongest resonant luminescence peak is obtained at 1524 nm. The enhancement factor is 110, and the corresponding Purcell factor is estimated to be 6.7. The large enhancement is due to high Purcell factor and high collection efficiency of modified L3 cavity verified by far-field patterns. The intrinsic Q factor measured from crossed-polarized resonant scattering is much higher than the Q factor measured from PL, indicating that the Q factors measured from PL are inaccurate due to free-carrier absorption of the photogenerated carriers.

SEM image of fabricated modified L3 cavity. The three holes adjacent to the cavity are laterally shifted by 0.175 a, 0.025 a, 0.175 a, respectively, shown with green arrows. Radius of the holes around the cavity, which were labeled by the red ovals, was reduced by a quantity of delta r 1/4 0:045 a to optimize the far fields of the cavity modes for stronger vertical radiation. Room temperature PL spectra of the sample, the excitation power is 16 muhbox{W}. Black, green, blue, red curves represent the PL spectrum of the unprocessed Si/Ge membrane, reference PhC region (without cavities), traditional L3 cavity and modified L3 cavity, respectively. The top panel shows the calculated resonant wavelengths of modified L3 cavity. SEM image of fabricated modified L3 cavity. The three holes adjacent to the cavity are laterally shifted by 0.175 a, 0.025 a, 0.175 a, respectively, shown with green arrows. Radius of the holes around the cavity, which were labeled by the red ovals, was reduced by a quantity of delta r 1/4 0:045 a to optimize the far fields of the cavity modes for stronger vertical radiation. Room temperature PL spectra of the sample, the excitation power is 16 muhbox{W}. Black, green, blue, red curves represent the PL spectrum of the unprocessed Si/Ge membrane, reference PhC region (without cavities), traditional L3 cavity and modified L3 cavity, respectively. The top panel shows the calculated resonant wavelengths of modified L3 cavity.

Published in:

IEEE Photonics Journal  (Volume:5 ,  Issue: 5 )