A combination of advanced light engineering concepts enables a substantial improvement in photon extraction efficiency of micro-cavity-based single-photon sources in the telecom O-band at ∼1.3 µm. We ...employ a broadband bottom distributed Bragg reflector (DBR) and a top DBR formed in a dielectric micropillar with an additional circular Bragg grating in the lateral plane. This device design includes a doped layer in pin-configuration to allow for electric carrier injection. It provides broadband (∼8-10 nm) emission enhancement with an overall photon-extraction efficiency of ∼83% into the upper hemisphere and photon-extraction efficiency of ∼79% within numerical aperture NA=0.7. The efficiency of photon coupling to a single-mode fiber reaches 11% for SMF28 fiber (with NA=0.12), exceeds 22% for 980HP fiber (with NA=0.2) and reaches ∼40% for HNA fiber (with NA=0.42) as demonstrated by 3D finite-difference time-domain modeling.
The results of complex studies of static and dynamic performance of 1550 nm range VCSELs, which were created by direct bonding (wafer fusion technique) InAlGaAs/InP optical cavity wafers with ...AlGaAs/GaAs distributed Bragg reflector wafers grown by molecular beam epitaxy, are presented. The VCSELs with a buried tunnel junction diameter less than 7 μm demonstrated a single-mode lasing with a side-mode suppression ratio more than 40 dB; however, at diameters less than 5 μm, a sharp increase in the threshold current is observed. It is associated to the appearance of a saturable absorber due to penetration of optical mode into the non-pumped regions of the active region. The maximum single-mode output optical power and the –3 dB modulation bandwidth reached 4.5 mW and 8 GHz, respectively, at 20°C. The maximum data rate at 20°C under non-return-to-zero on-off keying modulation was 23 Gb/s for a short-reach link based on single-mode fiber SMF-28. As the length of the optical link increased up to 2000 m, the maximum data rate dropped to 18 Gbit/s. The main factors affecting the high-speed operation and data transmission range are defined and discussed, and the further ways to overcome themit are proposed.
The results of experiments aimed at fabricating and studying the properties of photodetector structures based on single-layer graphene produced by chemical vapor deposition are presented. The ...configuration of a Ta
2
O
5
vertical microcavity with a resonance wavelength of about 850 nm and a lower dielectric SiO
2
/Ta
2
O
5
distributed Bragg reflector is taken as the base structure. The conditions for the transfer and fabrication of mesas in the graphene layer on the microcavity surface are optimized. The diagnostics by Raman spectroscopy of the structural quality of graphene after fabrication of the mesas in the graphene layer and contact pads are indicative of the single-layer structure of graphene with a low intensity of features in its spectrum, responsible for imperfection of the structure. The photocurrent is measured under local optical pumping.
—The possibility of using vertical-emitting lasers with intracavity contacts (IC-VCSEL) and a rhomboidal oxide current aperture for creating a non-zero magnetic field optically pumped atomic ...magnetometers (OPM) with a
133
Cs vapor cell for magnetoencephalographic (MEG) systems were demonstrated. Relative intensity noise (RIN) and polarization resolved RIN of the IC-VCSEL in the 895 nm range with different mirror losses (linewidth) in the frequency range from 1Hz to 100 kHz were experimentally investigated. Lasers with low mirror loss (narrow linewidth) have polarization resolved RIN comparable to amplitude noise. For IC-VCSEL with an output optical power of 0.8 mW and a linewidth of 55 MHz, the noise level measured is 148 dB/Hz in 1 Hz bandwidth at 40 kHz frequency. The ultimate sensitivity of OPM based on two-beam
M
Z
-scheme with studied VCSELs was estimated as ~11 fT/
.
The optical characteristics of vertical cylindrical micropillars with AlGaAs distributed Bragg reflectors and InAs/GaAs quantum dots, which are designed for the fabrication of single-photon sources, ...have been studied. The effect of parameters such as the inclination angle of sidewalls, partial oxidation of AlGaAs layers, and deviation of quantum dots from the central axis of a micropillar on the Purcell factor and the radiation extraction efficiency has been numerically simulated by the finite-difference time-domain method. The allowable ranges of the listed parameters have been determined for cylindrical vertical 920-nm micropillars. The comparison of the calculations performed with the refined refractive indices of the used materials at cryogenic temperatures with the measured characteristics of the fabricated micropillar structures has confirmed the adequacy of the used models.
The influence of the substrate temperature and the flux of In adatoms on the structural and optical characteristics of InAs quantum dots with a low surface density is experimentally studied. An ...increase in the substrate temperature under conditions of a high flux of In adatoms promotes an increase in their surface migration and a certain decrease in the density of the array of quantum dots (down to ~(1–2) × 10
10
cm
–2
), however, in this case a significant short-wavelength shift of the photoluminescence spectrum is observed despite an increase in lateral sizes of dots. A decrease in the incident flux of In adatoms at optimal substrate temperatures makes it possible to reduce the dot density more efficiently (down to ~(1–2) × 10
9
cm
–2
).
Abstract
We propose a hybrid microcavity design of a 1.3 μm range electrically driven single-photon source (SPS) consisting of two high-contrast dielectric distributed Bragg reflectors which surround ...a 3λ-thick semiconductor cavity with two intra-cavity contact layers and four 40-nm-thick oxide-confined apertures. According to 3D finite-difference time-domain modelling, the overall photon-extraction efficiency of ~74% and the Purcell factor of ~13 can be obtained by properly adjusting the position of oxide-confined apertures relative to the electric field of the fundamental optical mode. The studied SPS design also demonstrates a coupling efficiency of up to 13% within numerical aperture 0.12 in contrast to ~5% reached for a conventional semiconductor micropillar.
Mushroom mesa structure for InAlAs/InGaAs avalanche photodiodes (APD) was proposed and investigated. APD heterostructrures were grown by molecular-beam epitaxy. Fabricated APDs with the sensitive ...area diameter of about 30 micron were passivated by SiN deposition and demonstrated avalanche breakdown voltage
V
br
70–80 V. At the applied bias of 0.9
V
br
, the dark current was 75–200 nA. The single-mode coupled APDs demonstrated responsivity at a gain of unity higher than 0.5 A/W at 1550 nm.
The emission linewidth of single-mode vertical-cavity surface-emitting lasers with an active region based on strained InGaAs/InGaAlAs quantum wells in the spectral range of 1.55 μm was studied. The ...removal of degeneracy in polarization of the fundamental mode (splitting of the resonance wavelength) and polarization switching (type I) associated with the transition from lasing via the short-wavelength mode to lasing via the long-wavelength one were observed. As the output optical power increased, the emission linewidth dropped to ~30 MHz for both orthogonally polarized modes and was limited by the residual linewidth. The value of the α-factor was estimated: for the short-wavelength mode it reached 5, while for the long-wavelength mode it increased to ~9. At an output optical power of more than 1 mW, the emission line broadening is observed, which can be associated with a gain saturation and the increased α-factor caused by a strong self-heating of the investigated laser.
Abstract
Vertical-cavity surface-emitting lasers of 1.3 μm spectral range with the active region based on the InGaAs/InGaAlAs superlattice were studied. VCSEL heterostructure was formed by a ...wafer-fusion of the heterostructure with an active region and two DBRs grown by molecular-beam epitaxy on InP and GaAs substrates respectively. Fabricated VCSELs have shown threshold current below 1.6 mA and frequency of small signal modulation near 9 GHz at 20°C.
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