Radiation effects of heavy ions on the static and dynamic characteristics of 850 nm high-speed vertical cavity surface emitting lasers
Introduction
High speed vertical cavity surface emitting lasers (VCSELs ) have become the preferred light source for short distance transmission links due to their excellent characteristics, such as low threshold current, high-speed modulation, and good beam quality etc. [[1], [2], [3]]. At present, they are widely used in optical interconnects in harsh environments such as avionics, space, and high energy physics [[4], [5], [6]]. In addition, taking their advantages of both low divergence and low linewidth, VCSELs are promising candidates for optical links used in Earth-Satellites and Circular Electron-Positron Collider-Super Proton-Proton Collider (CEPC-SPPC) [5,6]. However, the VCSELs performance can be affected by high fluence particles with high energy in space and CEPC-SPPC [5,7,8]. Therefore, it is imperative to investigate the effect of various high-energy particles such as protons, neutrons and heavy ions on the reliabiity of high-speed VCSELs.
At present, extensive work has been devoted to evaluating radiation damage affecting the static characteristics of devices under various particles irradiation such as protons, neutrons, pions and ions [[9], [10], [11], [12], [13]]. A. Kalavagunta et al. illustrated that the threshold current and output power were degraded under proton irradiation caused by displacement damage effect [[9], [10], [11]], while the slope efficiency was almost unchanged [11]. J. Troska et al. pointed out that VCSELs are more radiation resistant than edge-emitting lasers and pions induce more damage than neutrons [9,12]. N. Venet et al. suggested that no irradiation damage occurs when heavy ion radiation fluence below 1 × 107 ions/cm2 [13]. However, the fluence level of heavy ion can be much higher in practical application, as for example the CEPC-SPPC will collide heavy ions with a fluence as high as 1010 ions/cm2 when it reachs its design performane [5]. In addition, only a few studies of dynamic properties of irradiated VCSELs have been carried out and the underlying mechanisms responsible for the radiation damage are yet to be fully understood. In order to analyze and improve the design of functional devices, a through understanding of radiation effects on irradiated VCSELs with high energy heavy ions is necessary.
In this paper, we examine for the first time the effect of 1907 MeV Ta ion on high-speed oxide-confined VCSEL. The static and dynamic characteristics of devices experienced ion fluences between 5 × 107–1 × 1010 ions/cm2 were investigated. The experimental results show that VCSELs are sensitive to radiation damage induced by heavy ions. The degradation of static characteristics can be attributed to enhanced carrier loss and optical absorption in both cavity and distributed-Bragg reflectors (DBRs). The unusual behavior of dynamic response can be explained in terms of degradation of both DBRs and active region.
Section snippets
Material and methods
The structure of the VCSELs investigated in this study is shown in Fig. 1. The VCSEL is designed for 850 nm operation with a 1.5-λ separate confinement heterostructure (SCH) region containing an active region with three 7 nm thick GaAs quantum wells (QWs) separated by 8 nm Al0.3Ga0.7As barriers. The SCH is sandwiched between a p-doped DBR containing 22 pairs of Al0.9Ga0.1As/Al0.12Ga0.88As and an n-doped DBR containing 34 pairs of Al0.9Ga0.1As/Al0.12Ga0.88As. One 30 nm thick Al0.98Ga0.02As layer
Static performance characteristics of VCSELs
In order to determine the irradiation effects on the device performance, the VCSELs with similar L-I-V and spectral characteristics as shown in Fig. 2 have been selected for followed radiation measurements to exclude wrong information induced by scattered device performance. The typical L-I-V characteristics of irradiated VCSELs are shown in Fig. 3 together with a pre-irradiated L-I-V curve for comparision. The important parameters of device performance including the threshold current Ith,
Conclusion
In conclusion, the radiation effects of 1907 MeV Ta ion on the static and dynamic characteristics of 850 nm VCSELs have been systemically investigated and corresponding mechanisms have been revealed. Our results clearly show that Ta ion radiation induces excessive defects resulting in enhanced carrier loss and optical absorption in both cavity and DBR mirrors. As a result, the static performance characteristics of devices after radiation including threshold current, output power and thermal
Funding
This work was supported by the National Natural Science Foundation of China, (Grants 61804175 and 61874135), Key Research Program of Frontier Sciences, Chinese Academy of Sciences, (No. ZDBS-LY-JSC031 & ZDBS-LY-JSC015), Innovation Center of Radiation Application Project, China Institute of Atomic Energy, (No. KFZC2018040203), Institute of Modern Physics Project, Chinese Academy of Sciences, (No. HIR19PY015).
Author statement
All authors have seen and approved the final version of the manuscript being submitted. We warrant that the article is the authors' original work, hasn't received prior publication and isn't under consideration for publication elsewhere.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
We thank the members of the HIRFL Accelerator at the Institute of Modern Physics, Chinese Academy of Sciences, for the sample irradiation.
References (28)
Theory of the electrical properties of germanium and silicon
Adv. Electron. Electron. Phys.
(1955)Forty years of vertical-cavity surface-emitting laser: invention and innovation
Jpn. J. Appl. Phys.
(2018)- et al.
Application of nanophotonics to the next generation of surface-emitting lasers
Nanophotonics
(2017) - et al.
Advanced VCSEL technology: self-heating and intrinsic modulation response
IEEE J. Quant. Electron.
(2018) - et al.
Radiation hard optical link developments at CERN
CEPC-SPPC Preliminary Conceptual Design Report
(2015)- et al.
Advances in VCSEL for satellite applications
- et al.
Cosmic rays-astronomy with energetic particles
Am. Inst. Phys.
(1974) Radiation effects in optoelectronic devices
IEEE Trans. Nucl.
(2013)- et al.
Radiation damage studies of lasers and photodiodes for use in multi-gb/s optical data links
IEEE Trans. Nucl. Sci.
(2011)
Radiation Hardness and Life Time Studies of LEDs and VCSELs for the Optical Readout of the ATLAS SCT
Effects of 2 MeV proton irradiation on operating wavelength and leakage current of vertical cavity surface emitting lasers
IEEE Trans. Nucl. Sci.
Laser and photodiode environmental evaluation for the Versatile Link project
J. Instrum.
Spaceflex onboard digital transparent processor: a new generation of DTP with optical digital interconnects
International Conference on Space Optics (ICSO)
Cited by (3)
Annealing effects of 850 nm vertical-cavity surface-emitting lasers after proton irradiation
2022, HeliyonCitation Excerpt :Many studies have been conducted on the parameter degradation of VCSELs under radiation. The radiation sources used include gamma rays, neutrons, protons, electrons, and heavy ions [11, 12, 13, 14, 15]. Although the earlier studies qualitatively explored experimental rules, later studies examined the physical mechanism of GaAs/AlGaAs material degradation [16].
Radiation effect and simulation of 850 nm vertical-cavity surface-emitting laser
2022, He Jishu/Nuclear Techniques