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Author

H.M. Shen

Bio: H.M. Shen is an academic researcher from Massachusetts Institute of Technology. The author has contributed to research in topics: Saturable absorption & Distributed Bragg reflector. The author has an hindex of 7, co-authored 15 publications receiving 257 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, the authors demonstrate a high-repetition-rate soliton fiber laser that is based on highly doped anomalously dispersive erbium-doped fiber.
Abstract: We demonstrate a high-repetition-rate soliton fiber laser that is based on highly doped anomalously dispersive erbium-doped fiber. By splicing an 11mm single-mode fiber to the erbium-doped fiber, the thermal damage of the butt-coupled saturable Bragg reflector (SBR) is overcome. The laser generates 187fs pulses at a repetition rate of 967MHz with a measured long-term stability of more than 60 h.

103 citations

Journal ArticleDOI
TL;DR: In this paper, a smooth unstructured supercontinuum between 1200 and 1800 nm is generated through a grating pair, and pulses, originally of 150-fs length, are compressed to 25 fs.
Abstract: Highly nonlinear normally dispersive bismuth-oxide fiber shows promise for applications such as supercontinuum generation and femtosecond pulse compression in the telecommunications-wavelength range. To generate a wideband and flat supercontinuum spectrum, the balance between fiber nonlinearity and normal group velocity dispersion (GVD) is important. Highly nonlinear bismuth-oxide fiber exhibits a large nonlinearity due to the small effective area and nonlinear index of the host glass material. The fiber also has a relatively flat dispersion profile over a large wavelength range. Utilizing these features, we generate a smooth unstructured supercontinuum between 1200 and 1800 nm. This supercontinuum is passed through a grating pair, and pulses, originally of 150-fs length, are compressed to 25 fs.

32 citations

Journal ArticleDOI
TL;DR: Large-area, broadband SBRs are used to self-start and mode lock a variety of laser systems at wavelengths from 800 to 1550 nm.
Abstract: Broadband saturable Bragg reflectors (SBRs) are designed and fabricated by monolithic integration of semiconductor saturable absorbers with broadband Bragg mirrors. The wet oxidation of AlAs creates low-index AlxOy layers for broadband, high-index-contrast AlGaAs/AlxOy or InGaAlP/AlxOy mirrors. SBR mirror designs indicate greater than 99% reflectivity over bandwidths of 294, 466, and 563 nm for center wavelengths of 800, 1300, and 1550 nm, respectively. Highly strained and unstrained absorbers are stably integrated with the oxidized mirrors. Large-scale lateral oxidation techniques permit the fabrication of SBRs with diameters of 500 µm. Large-area, broadband SBRs are used to self-start and mode lock a variety of laser systems at wavelengths from 800 to 1550 nm.

31 citations

Journal ArticleDOI
TL;DR: An ultrabroadband high-index-contrast saturable Bragg reflector consisting of a silicon/silicon dioxide/germanium structure that is fully compatible with CMOS processing is demonstrated, with what is to the authors' knowledge the broadest output spectrum to date.
Abstract: We demonstrate femtosecond performance of an ultrabroadband high-index-contrast saturable Bragg reflector consisting of a silicon/silicon dioxide/germanium structure that is fully compatible with CMOS processing. This device offers a reflectivity bandwidth of over 700 nm and subpicosecond recovery time of the saturable loss. It is used to achieve mode locking of an Er-Yb:glass laser centered at 1540 nm, generating 220-fs pulses, with what is to our knowledge the broadest output spectrum to date.

29 citations

Journal ArticleDOI
TL;DR: In this article, a 7-period GaAs/Al x O y Bragg mirror and an InGaAs/InP quantum well were used to start modelocking of 36 fs pulses near 1500 nm in a dispersion compensated Cr 4+ :YAG laser.

26 citations


Cited by
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Journal Article
TL;DR: The silicon chip has been the mainstay of the electronics industry for the last 40 years and has revolutionized the way the world operates as mentioned in this paper, however, any optical solution must be based on low-cost technologies if it is to be applied to the mass market.
Abstract: The silicon chip has been the mainstay of the electronics industry for the last 40 years and has revolutionized the way the world operates. Today, a silicon chip the size of a fingernail contains nearly 1 billion transistors and has the computing power that only a decade ago would take up an entire room of servers. As the relentless pursuit of Moore's law continues, and Internet-based communication continues to grow, the bandwidth demands needed to feed these devices will continue to increase and push the limits of copper-based signaling technologies. These signaling limitations will necessitate optical-based solutions. However, any optical solution must be based on low-cost technologies if it is to be applied to the mass market. Silicon photonics, mainly based on SOI technology, has recently attracted a great deal of attention. Recent advances and breakthroughs in silicon photonic device performance have shown that silicon can be considered a material onto which one can build optical devices. While significant efforts are needed to improve device performance and commercialize these technologies, progress is moving at a rapid rate. More research in the area of integration, both photonic and electronic, is needed. The future is looking bright. Silicon photonics could provide low-cost opto-electronic solutions for applications ranging from telecommunications down to chip-to-chip interconnects, as well as emerging areas such as optical sensing technology and biomedical applications. The ability to utilize existing CMOS infrastructure and manufacture these silicon photonic devices in the same facilities that today produce electronics could enable low-cost optical devices, and in the future, revolutionize optical communications

1,479 citations

Journal ArticleDOI
TL;DR: In this paper, the authors review various aspects of fabrication, characterization, device implementation and operation of carbon nanotube-polymer composites to be used in photonic applications.
Abstract: Polymer composites are one of the most attractive near-term means to exploit the unique properties of carbon nanotubes and graphene. This is particularly true for composites aimed at electronics and photonics, where a number of promising applications have already been demonstrated. One such example is nanotube-based saturable absorbers. These can be used as all-optical switches, optical amplifier noise suppressors, or mode-lockers to generate ultrashort laser pulses. Here, we review various aspects of fabrication, characterization, device implementation and operation of nanotube-polymer composites to be used in photonic applications. We also summarize recent results on graphene-based saturable absorbers for ultrafast lasers.

959 citations

Journal Article
TL;DR: In this paper, the authors provide an overview of the state of the art in silicon photonics and outline challenges that must be overcome before large-scale commercialization can occur, in particular, for realization of integration with CMOS very large scale integration (VLSI) and must operate within thermal constraints of VLSI chips.
Abstract: After dominating the electronics industry for decades, silicon is on the verge of becoming the material of choice for the photonics industry: the traditional stronghold of III-V semiconductors. Stimulated by a series of recent breakthroughs and propelled by increasing investments by governments and the private sector, silicon photonics is now the most active discipline within the field of integrated optics. This paper provides an overview of the state of the art in silicon photonics and outlines challenges that must be overcome before large-scale commercialization can occur. In particular, for realization of integration with CMOS very large scale integration (VLSI), silicon photonics must be compatible with the economics of silicon manufacturing and must operate within thermal constraints of VLSI chips. The impact of silicon photonics will reach beyond optical communication-its traditionally anticipated application. Silicon has excellent linear and nonlinear optical properties in the midwave infrared (IR) spectrum. These properties, along with silicon's excellent thermal conductivity and optical damage threshold, open up the possibility for a new class of mid-IR photonic devices

701 citations

Journal ArticleDOI
TL;DR: This work demonstrates that the photonic approach can deliver on its promise by digitizing a 41 GHz signal with 7.0 effective bits using a photonic ADC built from discrete components, a 4-5 times improvement over the performance of the best electronic ADCs which exist today.
Abstract: Accurate conversion of wideband multi-GHz analog signals into the digital domain has long been a target of analog-to-digital converter (ADC) developers, driven by applications in radar systems, software radio, medical imaging, and communication systems. Aperture jitter has been a major bottleneck on the way towards higher speeds and better accuracy. Photonic ADCs, which perform sampling using ultra-stable optical pulse trains generated by mode-locked lasers, have been investigated for many years as a promising approach to overcome the jitter problem and bring ADC performance to new levels. This work demonstrates that the photonic approach can deliver on its promise by digitizing a 41 GHz signal with 7.0 effective bits using a photonic ADC built from discrete components. This accuracy corresponds to a timing jitter of 15 fs - a 4-5 times improvement over the performance of the best electronic ADCs which exist today. On the way towards an integrated photonic ADC, a silicon photonic chip with core photonic components was fabricated and used to digitize a 10 GHz signal with 3.5 effective bits. In these experiments, two wavelength channels were implemented, providing the overall sampling rate of 2.1 GSa/s. To show that photonic ADCs with larger channel counts are possible, a dual 20-channel silicon filter bank has been demonstrated.

418 citations

Journal ArticleDOI
TL;DR: It is found that MoSe(2) exhibits highest modulation depth with similar preparation process among four saturable absorbers, which demonstrates the feasibility of TMDs to Q-switch fiber laser effectively.
Abstract: In this paper, we report 4 different saturable absorbers based on 4 transition metal dichalcogenides (MoS2, MoSe2, WS2, WSe2) and utilize them to Q-switch a ring-cavity fiber laser with identical cavity configuration. It is found that MoSe2 exhibits highest modulation depth with similar preparation process among four saturable absorbers. Q-switching operation performance is compared from the aspects of RF spectrum, optical spectrum, repetition rate and pulse duration. WS2 Q-switched fiber laser generates the most stable pulse trains compared to other 3 fiber lasers. These results demonstrate the feasibility of TMDs to Q-switch fiber laser effectively and provide a meaningful reference for further research in nonlinear fiber optics with these TMDs materials.

414 citations