Quantum Well Laser Diodes With Slightly-Doped Tunnel Junction

We experimentally investigate the electrical and optical characteristics of conventional quantum well laser diodes and the quantum well laser diodes with slightly-doped tunnel junction N++GaAs/undoped-GaAs. The results show that the slightly-doped tunnel junction give significant role on the laser diodes performances in the InGaAs/GaAs quantum well material system. The TJ LD has a internal quantum efficiency of 21% and the loss is 6.9 em -1 , the current threshold is 35 mA, both the lasers are operating at 1.06 μm, but the slightly-doped tunnel junction diode show nonlinear S-shaped current-voltage and broadband lasing characteristics. The results may also lead to the realization of more applications

Kicking the habit/semiconductor lasers without isolators

In this paper, we propose and demonstrate a solution to the problem of coherence degradation and collapse caused by the back reflection of laser power into the laser resonator. The problem is most onerous in semiconductor lasers (SCLs), which are normally coupled to optical fibers, and results in the fact that practically every commercial SCL has appended to it a Faraday-effect isolator that blocks most of the reflected optical power preventing it from entering the laser resonator. The isolator assembly is many times greater in volume and cost than the SCL itself. This problem has resisted a practical and economic solution despite decades of effort and remains the main obstacle to the emergence of a CMOS-compatible photonic integrated circuit technology. A simple solution to the problem is thus of major economic and technological importance. We propose a strategy aimed at weaning semiconductor lasers from their dependence on external isolators. Lasers with large internal Q-factors can tolerate large reflections, limited only by the achievable Q values, without coherence collapse. A laser design is demonstrated on the heterogeneous Si/III-V platform that can withstand 25 dB higher reflected power compared to commercial DFB lasers. Larger values of internal Qs, achievable by employing resonator material of lower losses and improved optical design, should further increase the isolation margin and thus obviate the need for isolators altogether

High-speed Coherent Optical Communication with Isolator-free Heterogeneous Si/III-V Lasers

Coherent optical communication is considered as an indispensable solution to the ever-increasing demand for higher data rates. To reduce the cost and form factor of coherent transceivers, full integration of photonic devices including lasers, modulators, amplifiers, photodetectors, and other components is necessary. However, as fabricating optical isolators on chip remains extremely challenging, optical feedback, which can degrade the coherence of semiconductor lasers, becomes the main obstacle, thwarting large-scale photonic integration. An appealing solution to such a problem is to use semiconductor lasers with intrinsic insensitivity to optical feedback as the integrated light sources. The heterogenous Si/III-V lasers, with their built-in high-Q resonators, are expected to possess a robustness to optical feedback which exceeds by several orders of magnitude compared to commercial III-V distributed feedback (DFB) lasers, which will be validated here. We present data showing that the heterogeneous Si/III-V lasers can preserve their phase coherence under much larger optical feedback and therefore function without severe degradation in isolator-free coherent optical communication systems

Quantum Well Laser-Based Optical Bistable Switching Device

Quantum well laser-based bistable switching lasers with low lasing threshold current densities and good electrical turn-on properties have been produced. The electrical properties of the devices are analyzed. It is found that this type of device possesses bistable characteristics providing an realization of devices for switching applications

Hybrid Integration of a Tunneling Diode and a 1310 nm DFB Semiconductor Laser

We experimentally demonstrate a InP-based hybrid integration of a single-mode DFB laser emitting at around 1310 nm and a tunneling diode. The evident negative differential resistance regions were explored in both electrical and optical output characteristics. The electrical and optical bistability controlled by the voltage through the tunneling diode were measured. When the voltage changes between 1.46 V and 1.66 V, a 200-mV-wide hysteresis loop was formed and an optical power on/off ratio of 17 dB was obtained. A side-mode suppression ratio of the integrated device in the “on” state is up to 43 dB. Compared to directly controlled by a voltage source, the tunneling diode can switch on/off the laser within a very small voltage range

Investigation of InGaAs/GaAs Quantum Well Lasers with Slightly Doped Tunnel Junction

We experimentally investigate and analyze the electrical and optical characteristics of InGaAs/GaAs conventional quantum well laser diode and the quantum well laser diode with slightly-doped tunnel junction. It was found that the laser with slightly-doped tunnel junction has a nonlinear S-shape current-voltage characteristic. The internal quantum efficiencies of the laser with slightly-doped tunnel junction and the conventional laser are 21 and 87.3%, respectively. This suggests that the slightly-doped tunnel junction increased the barrier width and free carrier absorption, thus could reduce the electron tunneling probability and increase the internal loss. Furthermore, compared with the conventional laser, it was found that we could achieve 15 nm broadband spectrum from the laser with slightly-doped tunnel junction, due to the lasing dynamics reflecting the current dynamics. The results show that the slightly-doped tunnel junction plays a crucial role in the laser diode performances, which may lead to the realization of more applications

Coherent and Incoherent Optical Feedback Sensitivity of High-coherence Si/III-V Hybrid Lasers

We demonstrate that high-coherence Si/III-V hybrid lasers are much more robust than conventional III-V DFB lasers against both coherent and incoherent optical feedback by examining the frequency noise power spectral density of the lasers

Investigation of InGaAs/GaAs Quantum Well Lasers with Slightly Doped Tunnel Junction

We experimentally investigate and analyze the electrical and optical characteristics of InGaAs/GaAs conventional quantum well laser diode and the quantum well laser diode with slightly-doped tunnel junction. It was found that the laser with slightly-doped tunnel junction has a nonlinear S-shape current-voltage characteristic. The internal quantum efficiencies of the laser with slightly-doped tunnel junction and the conventional laser are 21 and 87.3%, respectively. This suggests that the slightly-doped tunnel junction increased the barrier width and free carrier absorption, thus could reduce the electron tunneling probability and increase the internal loss. Furthermore, compared with the conventional laser, it was found that we could achieve 15 nm broadband spectrum from the laser with slightly-doped tunnel junction, due to the lasing dynamics reflecting the current dynamics. The results show that the slightly-doped tunnel junction plays a crucial role in the laser diode performances, which may lead to the realization of more applications

Hybrid Integration of a Tunneling Diode and a 1310 nm DFB Semiconductor Laser

We experimentally demonstrate a InP-based hybrid integration of a single-mode DFB laser emitting at around 1310 nm and a tunneling diode. The evident negative differential resistance regions were explored in both electrical and optical output characteristics. The electrical and optical bistability controlled by the voltage through the tunneling diode were measured. When the voltage changes between 1.46 V and 1.66 V, a 200-mV-wide hysteresis loop was formed and an optical power on/off ratio of 17 dB was obtained. A side-mode suppression ratio of the integrated device in the “on” state is up to 43 dB. Compared to directly controlled by a voltage source, the tunneling diode can switch on/off the laser within a very small voltage range