In0.52Al0.48As based top-illuminated APDs with a dual-multiplication layer design is demonstrated. It can deliver high output photocurrent (12.7 mA) with high-responsivity (6.3 A/W) and high single-photon detection efficiency (48% @ 300K) with short jitter (65 ps) under 0.9 Vbr and Geiger-mode operation, respectively.
New applications in industrial, automotive and datacom applications require vertical-cavity surface-emitting lasers (VCSELs) operating at very high ambient temperatures at ultrahigh speed. We discuss issues related to high temperature performance of the VCSELs including temperature response and spectral properties. The influence of the gain-to-cavity wavelength detuning on temperature performance and spectral width of the VCSELs is discussed. Performance of the oxide-confined 850 nm VCSELs with increased temperature stability capable of operating at bit rates up to 25 Gbit/s at heat sink temperature of 150°C and 35Gbit/s at 130°C. Furthermore, opposite to previous studies of VCSELs with large gain-to-cavity detuning, which demonstrated strongly increased spectral width and a strong redistribution of the mode intensities upon current increase. VCSELs demonstrated in this work show good reproducibility of a narrow spectrum in a wide range of currents and temperatures. Such performance strongly improves the transmission distance over multi-mode fiber and can reduce mode partition noise during high speed operation.
The development of advanced OM5 wideband multimode fiber (WBMMF) allowing high modal bandwidth in the spectral range 840-950 nm motivates research in vertical-cavity-surface-emitting-lasers (VCSELs) at wavelengths beyond the previously accepted for short reach communications. Thus, short wavelength division multiplexing (SWDM) solutions can be implemented as a strategy to satisfy the increasing demand of data rate in datacenter environments. As an alternative solution to 850 nm parallel links, four wavelengths with 30 nm separation between 850 nm and 940 nm can be multiplexed on a single OM5-MMF, so the number of fibers deployed is reduced by a factor of four. In this paper high speed transmission is studied for VCSELs in the 850 nm – 950 nm range. The devices had a modulating bandwidth of ~26-28 GHz. 50 Gb/s non-return-to-zero (NRZ) operation is demonstrated at each wavelength without preemphasis and equalization, with bit-error-rate (BER) below 7% forward error correction (FEC) threshold. Furthermore, the use of single-mode VCSELs (SM-VCSELs) as a way to mitigate the effects of chromatic dispersions in order to extend the maximum transmission distance over OM5 is explored. Analysis of loss as a function of wavelength in OM5 fiber is also performed. Significant decrease is observed, from 2.2 dB/km to less than 1.7 dB/km at 910 nm wavelength of the VCSEL.
Vertical-cavity surface-emitting lasers (VCSELs) has become the most important light source in the booming market of short-reach (< 300 meters) optical interconnect (OI). The next generation OI has been targeted at 56 Gbit/sec data rate per channel (CEI-56G) with the total data rate up to 400 Gbit/sec. However, the serious modal dispersion of multi-mode fiber (MMF), limited speed of VCSEL, and its high resistance (> 150 Ω) seriously limits the >50 Gbit/sec linking distance (< 10 m) by using only on-off keying (OOK) modulation scheme without any signal processing techniques. In contrast to OOK, 4-PAM modulation format is attractive for >50 Gbit/sec transmission due to that it can save one-half of the required bandwidth. Nevertheless, a 4.7 dB optical power penalty and the linearity of transmitter would become issues in the 4-PAM linking performance. Besides, in the modern OI system, the optics transreceiver module must be packaged as close as possible with the integrated circuits (ICs). The heat generated from ICs will become an issue in speed of VSCEL. Here, we review our recent work about 850 nm VCSEL, which has unique Zn-diffusion/oxide-relief apertures and special p- doping active layer with strong wavelength detuning to further enhance its modulation speed and high-temperature (85°C) performances. Single-mode (SM) devices with high-speed (~26 GHz), reasonable resistance (~70 Ω) and moderate output power (~1.5 mW) can be achieved. Error-free 54 Gbit/sec OOK transmission through 1km MMF has been realized by using such SM device with signal processing techniques. Besides, the volterra nonlinear equalizer has been applied in our 4-PAM 64 Gbit/sec transmission through 2-km OM4 MMF, which significantly enhance the linearity of device and outperforms fed forward equalization (FFE) technique. Record high bit-rate distance product of 128⋅km is confirmed for optical-interconnect applications.
High-speed and “green” ~850 nm vertical-cavity surface-emitting lasers (VCSELs) have lately attracted lots of attention due to their suitability for applications in optical interconnects (OIs). To further enhance the speed and its maximum allowable linking distance of VCSELs are two major trends to meet the requirement of OI in next generation data centers. Recently, by use of the advanced 850 nm VCSEL technique, data rate as high as 64 Gbit/sec over 57m and 20 Gbit/sec over 2km MMF transmission have been demonstrated, respectively. Here, we will review our recent work about 850 nm Zn-diffusion VCSELs with oxide-relief apertures to further enhance the above-mentioned performances. By using Zn-diffusion, we can not only reduce the device resistance but also manipulate the number of optical modes to benefit transmission. Combing such device, which has excellent single-mode (SMSR >30 dB) and high-power (~7mW) performance, with advanced modulation format (OFDM), record-high bit-rate-distance-product through MMF (2.3 km×28 Gbit/sec) has been demonstrated. Furthermore, by selective etching away the oxide aperture inside Zn-diffusion VCSEL, significant enhancement of device speed, D-factor, and reliability can be observed. With such unique VCSEL structure, >40 Gbit/sec energy-efficient transmission over 100m MMF under extremely low-driving current density (<10kA/cm2) has been successfully demonstrated.
Due to the high attenuation in vitreous silica, acoustic attenuations in the THz regime are typically measured by
incoherent techniques such as Raman, neutron, and X-ray scattering. Here, we utilized multiple-quantum-well structures
to demonstrate acoustic spectroscopy of vitreous silica up to THz regime. The acoustic properties of silica thin films
prepared by chemical deposition methods were characterized in the sub-THz regime. This technique may be useful in
resolving debated issues relating to Boson peak around 1 THz.
The mechanism responsible for the efficiency droop in AlGaInP based vertically-structured red light-emitting diodes
(LEDs) is investigated using dynamic measurement techniques. Short electrical pulses (~100ps) are pumped into this
device and the output optical pulses probed using high-speed photo-receiver circuits. From this, the internal carrier
dynamic inside the device can be investigated by use of the measured electrical-to-optical (E-O) impulse responses.
Results show that the E-O responses measured under different bias currents are all invariant from room temperature to
~100°. This is contrary to most results reported for AlGaInP based red LEDs, which usually exhibit a shortening in the
response time and degradation in output power with the increase of ambient temperature. According to these
measurement results and the extracted fall-time constants of the E-O impulse responses, the origin of the efficiency droop
in our vertical LED structure, which has good heat-sinking, is not due to thermally induced carrier leakage, but rather
should be attributed to defect recombination and the saturation of spontaneous recombination processes.
To provide integrated and high quality broadband services, higher carrier frequencies are required in wireless
communications. Currently, there is a great deal of interests in wireless communications at sub-terahertz or terahertz
frequencies, i.e., the millimeter-wave (MMW) or sub-millimeter-wave (sub-MMW). In this work, we will discuss our
recent advances in millimeter-wave photonic wireless links for high data rate (10 - 20 Gb/s) communications. The
concept of fiber-to-the-antenna (FTTA) system using radio-over-fiber (ROF) technologies will be given in the
introduction. Then a design and the structure of the high speed MMW photonic transmitter, namely near-ballistic unitraveling-
carrier photodiode (NBUTC-PD), will be discussed in section 2. In section 3, the operation principle of
photonic mm-wave waveform generator (PMWG), which is used to produce the optical pulse train for the photonic
transmitter at the antenna-site will be illustrated. We then demonstrate the use of the NBUTC-PD and the PMWG for the
downstream and upstream high data rate communications in the W-band.
In this research, we demonstrate array of transverse-junction (TJ) blue light-emitting-diodes (LEDs), which are specified
as a horizontal carrier flow instead of side-by-side injection, with a consequence of InxGa1-xN/GaN multiple-quantumwells
(MQWs) as the active region. The demonstrated devices were carried out by the re-growth of n-type GaN on the
sidewall of p-type GaN. Regarding the transverse carrier flow of injected carriers, these TJ-LEDs, as compared to the
control related to traditional vertical junction structure, can effectively spread injected currents more uniformly,
minimize the problem of nonuniform carrier-distribution and current crowding effect, and achieve 35% improvement of
power performance.
The two major trends in the development of photodetectors (PDs) are improving bandwidth-efficiency product and obtaining high output power-bandwidth product. In this invited paper we review our recent work on PDs, which can meet these two challenges simultaneously, for the applications of 40-Gb/s long-haul and 10-Gb/s short-reach fiber communication.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.