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Low levels of intensity noise in semiconductor lasers is a key feature for numerous applications such as high resolution spectroscopy, fiber-optic sensors, signal distribution in broadband analog communications as CATV, and more generally for microwave photonics systems. In particular, a DFB laser with very low relative intensity noise (RIN) levels...
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In this paper we discuss the development of new semiconductor materials and approaches to overcome the fundamental limitations of well established (Al, In)GaAs/InP and InGaAsP/InP infrared-emitting lasers. We consider three approaches; dilute nitride InGaAsN-based structures; InAs-based quantum dot/dash structures and the most recently emerging dil...
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... H IGH-POWER 1.55 µm single-mode distributed feedback (DFB) lasers have various applications, such as silicon photonics technology, free space optical (FSO) communications [1], [2], [3], light detection, and ranging (LiDAR) systems [4], [5], [6]. In addition, a low relative intensity noise (RIN) level in high-power single-mode DFB lasers is of vital significance in microwave photonics systems [7], [8]. ...
A gain-coupled high-power low-RIN
$1.55~\mu \text{m}$
single-mode distributed feedback (DFB) laser with a 6-
$\mu \text{m}$
-wide ridge waveguide is demonstrated based on an optimized double trench ridge waveguide structure. Gain-coupling mechanism is implemented by carrier-injection gratings. The impact of the doping concentration and thickness variations in the p-InP spacer layer on the carrier density ripple within the active region is investigated to achieve a large gain-coupling coefficient. The fabricated DFB laser exhibits a ~ 220 mW kink-free output power with a relative intensity noise (RIN) below −166 dB/Hz at 25°C. The side-mode suppression-ratio (SMSR) is about 60 dB and the far-field full-width-at-half-maximum (FWHM) divergence angles are
$10^{\circ }\times 20^{\circ }$
.
... High power semiconductor lasers working around 1550 nm have broad range applications, including free space optical (FSO) communication, silicon photonics (SiPh) co-packaged optics, coherent fiber optical communication, light detection and ranging (LiDAR) systems, etc., due to the low loss in optical fibers and atmosphere as well as 1-W level at "eye-safe" wavelengths near 1550 nm compared to 980 nm [1][2][3][4][5]. In addition, a low RIN level in semiconductor lasers is a key parameter for numerous applications such as high-resolution spectroscopy, fiber-optic sensors, signal distribution in broadband analog communications as CATV, and more generally for microwave photonics systems [6]. ...
... A lot of work has been done in the past on high power, single mode, low RIN and narrow linewidth semiconductor lasers for optical communication [6][7][8][9][10][11][12][13][14] as seen in Table 1. To keep single mode operation a narrow ridge waveguide structure is preferred for these lasers. ...
... At the same time, J.-R. Burie et al. have obtained 1.5-mm-long lasers with the output power of 130 mW and the RIN <−165 dB/Hz [6]. Adopting slab-coupled optical waveguide external cavity laser (SCOW-ECL) with an area of 16×6 in 2 , William Loh et al. have achieved 370 mW output power, 1 kHz linewidth and RIN <−160 dB/Hz at 16°C [10]. ...
We present an 8-µm-wide 800-µm-long high-power, single-mode and low RIN DFB laser using a dual-waveguide structure. The introduced passive lower waveguide has weakenes the lateral optical confinement for the ridge waveguide, and thus reduces losses caused by the p-doped layers and maintains single mode stability of the laser. The fabricated laser exhibited an output power higher than 170 mW and a relative intensity noise (RIN) below −157 dB/Hz along with a side-mode suppression-ratio (SMSR) over 55 dB. The temperature tuning from −10°C to 60°C allows an 8.6 nm wavelength tunability with a variation coefficient of 0.12 nm/K. The relaxation oscillation frequency is around 8 GHz, and the linewidth is about 250 kHz at 100 mW output power for the fabricated laser. The characteristics of the proposed high-power laser, including high slope efficiency, single mode stability and low noise, make it a suitable candidate for optical communication.
... For such lasers, it is possible to directly modulate the output of the laser (at GHz speeds) by varying the electrical power input. These lasers are commercially available (examples: Finisar DM 80, Emcore Medallion, Fitel FOL15DDBA), and have been fabricated by many research groups as well [Faugeron et al. 2012;Huang et al. 2008;Burie et al. 2010;]. The crucial issue in designing DML lasers is thermal stability. ...
Numerous challenges present themselves when scaling traditional on-chip electrical networks to large manycore processors. Some of these challenges include high latency, limitations on bandwidth, and power consumption. Researchers have therefore been looking for alternatives. As a result, on-chip nanophotonics has emerged as a strong substitute for traditional electrical NoCs.
As of 2017, on-chip optical networks have moved out of textbooks and found commercial applicability in short-haul networks such as links between servers on the same rack or between two components on the motherboard. It is widely acknowledged that in the near future, optical technologies will move beyond research prototypes and find their way into the chip. Optical networks already feature in the roadmaps of major processor manufacturers and most on-chip optical devices are beginning to show signs of maturity.
This article is designed to provide a survey of on-chip optical technologies covering the basic physics underlying the operation of optical technologies, optical devices, popular architectures, power reduction techniques, and applications. The aim of this survey article is to start from the fundamental concepts and move on to the latest in the field of on-chip optical interconnects.
... A lot of work has been done in the past on large bandwidth, medium power directly modulated lasers for digital and analog signal transmission [2], [3]. Impressive work was also done on continuous wave (CW) high power lasers for external modulation (140 mW @ 400 mA, RIN ≈ −161 dB/Hz @ 860 MHz, 400 mA) [4], (125 mW @ 1 A, RIN <−165 dB/Hz on the 0.1-20 GHz range @ 1 A) [5], pumping (1.2 W @ 5 A, λ = 1.48 μm) [6], (860 mW @ 4.8 A, λ = 1.5 μm) [7] and high power external cavity lasers (370 mW @ 4 A, RIN < −160 dB/Hz on the range 200 kHz−10 GHz) [8]. ...
... Combined with a high power photodiode it should permit to reach very high SFDR (Spurious-Free Dynamic Range) [16]. We expect to improve the fiber coupling by using more specific coupling systems and by circularizing the optical mode [5]. Lastly some modifications in process and mounting should permit to increase current polarization point and decrease thermal rollover at high power. ...
We report the demonstration of high-power and low relative intensity noise (RIN) directly modulated distributed feedback lasers at 1.55 $\mu{\rm m}$. We have developed a structure with asymmetrical cladding to reduce internal losses due to the p-doped upper cladding. We obtain an output power of 140 mW at 550 mA and an RIN below ${-}{\rm 157}~{\rm dB}/{\rm Hz}$ in the 0.1–20 GHz range along with a high side-mode suppression ratio $({>}{\rm 55}~{\rm dB})$ . The modulation bandwidth was larger than 7 GHz. The characteristics of these lasers, namely a high electrical to optical conversion efficiency (0.340 W/A at 350 mA), low noise, high power (98 mW at 350 mA), and linearity, make them the perfect candidates for high gain, high dynamic directly modulated analog links.
In this letter, we experimentally demonstrated a 1550-nm high-power single-longitudinal-mode (SLM) distributed feedback (DFB) semiconductor laser based on sampled moiré grating (SMG). By designing sampling structure with micrometer scale, moiré grating (MG) can be equivalently realized along laser cavity. Then, we can reduce coupling coefficient near laser facet so as to increase output power. The cavity length and ridge width of the fabricated laser are 1.0 mm and 3.0 μ m, respectively. The measured threshold current and the slope efficiency are 30.0 mA and 0.36 mW/mA at the heat-sink temperature of 25 oC, respectively. When the injection current is 800.0 mA, the maximum output power is about 183.0 mW. The saturation power is significantly improved compared with conventional DFB laser with uniform sampled grating (USG), which was fabricated on the same wafer. In addition, a four-channel DFB laser array based on SMG was also fabricated on the same wafer, showing good wavelength uniformity.
Following the increasing availability of reliable optical components, issued from the telecom domain, analog-optical links based on commercial modules have achieved performances which are close enough to system requirements to be extensively considered. With accurate understanding and modeling of these components, it has been demonstrated that RF photonics can be implemented to transmit and process RF signals in equipment. We report on recent progress concerning the development of several photonic modules to implement transmissions of radar (and electronic-warfare) signals in airborne environment.
In this thesis, we have studied a Radio-over-Fibre Distributed Antenna System for WLAN IEEE802.11g OFDM at 2.45 GHz. By analyzing the model and the characteristics of the optical link, we have studied the limitations of such system, and then proposed the technical solution. Because of the high noise figure and the low compression point of the optical link, the dynamic range of a Point to Point Radio-over-Fibre system could be very small, which does limit the performance of receiver (Access Point). Considering the received sensitivities defined by IEEE802.11g OFDM, the uplink could only respect the specification with the automatic gain control (AGC) loops. With simulation and measurement, we have proved that, using the automatic gain control units, the uplink performance of the access point can be improved. Then, we have analyzed the performance of the system including several distributed antennas. The uplink performance is still limited. For several architectures, we have studied the link budget and system dimensioning with different number of antennas. The diversity reception seemed necessary.
Code smells are manifestations of design flaws that can degrade code maintainability. As such, the existence of code smells seems an ideal indicator for maintainability assessments. However, to achieve comprehensive and accurate evaluations based on code smells, we need to know how well they reflect factors affecting maintainability. After identifying which maintainability factors are reflected by code smells and which not, we can use complementary means to assess the factors that are not addressed by smells. This paper reports on an empirical study that investigates the extent to which code smells reflect factors affecting maintainability that have been identified as important by programmers. We consider two sources for our analysis: (1) expert-based maintainability assessments of four Java systems before they entered a maintenance project, and (2) observations and interviews with professional developers who maintained these systems during 14 working days and implemented a number of change requests.
Following the increasing availability of reliable optical components, issued from the telecom domain, RF-optical links based on commercial modules have achieved performances which are close enough to system requirements to be extensively considered. With accurate understanding and modeling of these components, it has been demonstrated that RF photonics can be implemented to transmit and process RF signals in equipments. We report on recent progress concerning the development of several photonic modules to implement transmission of radar and EW signals in airborne environment.
