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Featured researches published by Youfang Hu.


IEEE Photonics Technology Letters | 2012

50-Gb/s Silicon Optical Modulator

David J. Thomson; F. Y. Gardes; Jean-Marc Fedeli; Sanja Zlatanovic; Youfang Hu; Bill P.-P. Kuo; Evgeny Myslivets; Nikola Alic; Stojan Radic; Goran Z. Mashanovich; Graham T. Reed

Optical modulators formed in silicon are the keystone to many low cost optical applications. Increasing the data rate of the modulator benefits the efficiency of channel usage and decreases power consumption per bit of data. Silicon-based modulators which operate via carrier depletion have to the present been demonstrated at data rates up to 40 Gb/s; however, here we present for the first time optical modulation at 50 Gb/s with a 3.1-dB extinction ratio obtained from carrier depletion based phase shifter incorporated in a Mach-Zehnder interferometer. A corresponding optical insertion loss of approximately 7.4 dB is measured.


Optics Express | 2011

High contrast 40Gbit/s optical modulation in silicon

David J. Thomson; F. Y. Gardes; Youfang Hu; Goran Z. Mashanovich; M. Fournier; P. Grosse; J.-M. Fedeli; Graham T. Reed

Data interconnects are on the verge of a revolution. Electrical links are increasingly being pushed to their limits with the ever increasing demand for bandwidth. Data transmission in the optical domain is a leading candidate to satisfy this need. The optical modulator is key to most applications and increasing the data rate at which it operates is important for reducing power consumption, increasing channel bandwidth limitations and improving the efficiency of infrastructure usage. In this work silicon based devices of lengths 3.5mm and 1mm operating at 40Gbit/s are demonstrated with extinction ratios of up to 10dB and 3.5dB respectively. The efficiency and optical loss of the phase shifter is 2.7V.cm and 4dB/mm (or 4.5dB/mm including waveguide loss) respectively.


Optics Express | 2011

Low loss silicon waveguides for the mid-infrared

Goran Z. Mashanovich; Milan M. Milosevic; Milos Nedeljkovic; N. Owens; Boqian Xiong; Ee Jin Teo; Youfang Hu

Silicon-on-insulator (SOI) has been used as a platform for near-infrared photonic devices for more than twenty years. Longer wavelengths, however, may be problematic for SOI due to higher absorption loss in silicon dioxide. In this paper we report propagation loss measurements for the longest wavelength used so far on SOI platform. We show that propagation losses of 0.6-0.7 dB/cm can be achieved at a wavelength of 3.39 µm. We also report propagation loss measurements for silicon on porous silicon (SiPSi) waveguides at the same wavelength.


Nanophotonics | 2014

Recent breakthroughs in carrier depletion based silicon optical modulators

Graham T. Reed; Goran Z. Mashanovich; F. Y. Gardes; Milos Nedeljkovic; Youfang Hu; David J. Thomson; Ke Li; Peter R. Wilson; Sheng-Wen Chen; Shawn S. Hsu

Abstract The majority of the most successful optical modulators in silicon demonstrated in recent years operate via the plasma dispersion effect and are more specifically based upon free carrier depletion in a silicon rib waveguide. In this work we overview the different types of free carrier depletion type optical modulators in silicon. A summary of some recent example devices for each configuration is then presented together with the performance that they have achieved. Finally an insight into some current research trends involving silicon based optical modulators is provided including integration, operation in the mid-infrared wavelength range and application in short and long haul data transmission links.


Optical Materials Express | 2013

Silicon photonic devices and platforms for the mid-infrared

Milos Nedeljkovic; Ali Z. Khokhar; Youfang Hu; Xia Chen; Jordi Soler Penades; Stevan Stanković; Harold Chong; David J. Thomson; F. Y. Gardes; Graham T. Reed; Goran Z. Mashanovich

Due to its excellent electronic and photonic properties, silicon is a good candidate for mid-infrared optoelectronic devices and systems that can be used in a host of applications. In this paper we review some of the results reported recently, and we also present several new results on mid-infrared photonic devices including Mach-Zehnder interferometers, multimode interference splitters and multiplexers based on silicon-on-insulator, polysilicon, suspended silicon, and slot waveguide platforms.


IEEE Photonics Technology Letters | 2010

Low Loss MMI Couplers for High Performance MZI Modulators

David J. Thomson; Youfang Hu; Graham T. Reed; Jean-Marc Fedeli

Optical splitters and combiners which can provide precise splitting with low loss, high thermal stability, large optical bandwidth, high compactness, and insensitivity to fabrication tolerances are essential components for high performance Mach-Zehnder Interferometers (MZI)-based optical modulators. In this letter, we theoretically and experimentally investigate the multimode interference (MMI) based structure and the reduction in optical loss achievable through the use of linear tapers at the input and output ports. Our data shows that losses can be reduced to below 1 dB/MMI without affecting the static extinction when employed in MZIs.


IEEE Journal of Selected Topics in Quantum Electronics | 2013

High Performance Mach–Zehnder-Based Silicon Optical Modulators

David J. Thomson; F. Y. Gardes; Sheng Liu; H. Porte; Lars Zimmermann; Jean-Marc Fedeli; Youfang Hu; Milos Nedeljkovic; Xin Yang; Periklis Petropoulos; Goran Z. Mashanovich

Silicon photonics is poised to revolutionize several data communication applications. The development of high performance optical modulators formed in silicon is essential for the technology to be viable. In this paper, we review our recent work on carrier-depletion silicon Mach-Zehnder-based optical modulators which have formed part of the work within the U.K. Silicon Photonics and HELIOS projects, as well as including some recent new data. A concept for the self-aligned formation of the p-n junction which is flexible in the capability to produce a number of device configurations is presented. This process is the key in having performance repeatability, a high production yield, and large extinction ratios. Experimental results from devices which are formed through such processes are presented with operation up to and beyond 40 Gbit/s. The potential for silicon photonics to fulfill longer haul applications is also explored in the analysis of the chirp produced from these devices and the ability to produce large extinction ratios at high speed. It is shown that the chirp produced with the modulator operated in dual drive configuration is negligible and that an 18-dB dynamic modulation depth is obtainable at a data rate of 10 Gbit/s.


IEEE Journal of Selected Topics in Quantum Electronics | 2015

Silicon Photonic Waveguides and Devices for Near- and Mid-IR Applications

Goran Z. Mashanovich; F. Y. Gardes; David J. Thomson; Youfang Hu; Ke Li; Milos Nedeljkovic; Jordi Soler Penades; Ali Z. Khokhar; Colin J. Mitchell; Stevan Stanković; R.P. Topley; Scott Reynolds; Yun Wang; Benedetto Troia; Vittorio M. N. Passaro; Callum G. Littlejohns; Thalia Dominguez Bucio; Peter R. Wilson; Graham T. Reed

Silicon photonics has been a very buoyant research field in the last several years mainly because of its potential for telecom and datacom applications. However, prospects of using silicon photonics for sensing in the mid-IR have also attracted interest lately. In this paper, we present our recent results on waveguide-based devices for near- and mid-infrared applications. The silicon-on-insulator platform can be used for wavelengths up to 4 μm; therefore, different solutions are needed for longer wavelengths. We show results on passive Si devices such as couplers, filters, and multiplexers, particularly for extended wavelength regions and finally present integration of photonics and electronics integrated circuits for high-speed applications.


Optics Letters | 2011

Wavelength division (de)multiplexing based on dispersive self-imaging

Youfang Hu; R. M. Jenkins; F. Y. Gardes; E. D. Finlayson; Goran Z. Mashanovich; Graham T. Reed

We proposed and experimentally demonstrated wavelength division (de)multiplexers (WDMs) utilizing the wavelength dispersive nature of self-imaging multimode interferometers. Proof-of-principle devices fabricated on the silicon-on-insulator platform operated as 4-channel WDMs with a free spectral range of >90 nm, an averaging cross talk of <-20 dB for a 1 nm band, and an insertion loss of <2.0 dB. The potential for higher channel counts and smaller channel wavelength spacing was also predicted. This type of WDM is easy to design and fabricate. The underlying concept is applicable to all planar waveguide platforms.


Nature Photonics | 2015

Device-level characterization of the flow of light in integrated photonic circuits using ultrafast photomodulation spectroscopy

Roman Bruck; Ben Mills; Benedetto Troia; David J. Thomson; F. Y. Gardes; Youfang Hu; Goran Z. Mashanovich; Vittorio M. N. Passaro; Graham T. Reed; Otto L. Muskens

Advances in silicon photonics have resulted in rapidly increasing complexity of integrated circuits. New methods are desirable that allow direct characterization of individual optical components in-situ, without the need for additional fabrication steps or test structures. Here, we present a new device-level method for characterization of photonic chips based on a highly localized modulation in the device using pulsed laser excitation. Optical pumping perturbs the refractive index of silicon, providing a spatially and temporally localized modulation in the transmitted light enabling timeand frequency-resolved imaging. We demonstrate the versatility of this all-optical modulation technique in imaging and in quantitative characterization of a variety of properties of silicon photonic devices, ranging from group indices in waveguides, quality factors of a ring resonator to the mode structure of a multimode interference device. Ultrafast photomodulation spectroscopy provides important information on devices of complex design, and is easily applicable for testing on the device-level. Integrated silicon-based photonics has developed into a mature technology platform with a multitude of applications [1-4], including telecommunications, healthcare diagnostics and optical sensors. As technology progresses, device designs become increasingly complex and integrate more functions onto a single device [5]. Characterization of fabricated devices is an important step in the design cycle as it highlights differences between the intended design

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Graham T. Reed

University of Southampton

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Ali Z. Khokhar

University of Southampton

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Scott Reynolds

University of Southampton

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Bernhard Goll

Vienna University of Technology

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