Tunable terahertz wave generation through a bimodal laser diode and plasmonic photomixer

Yang, Seungmi; Watts, Regan; Li, X.; Wang, N.; Cojocaru, V.; O’Gorman, J.; Barry, Liam P.; Jarrahi, Mona

doi:10.1364/oe.23.031206

Cited by 48 publications

(30 citation statements)

References 33 publications

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“…As a result, most of the photo-generated carriers drift to the nano-antennas within a sub-picosecond time-scale and contribute to enhanced terahertz radiation. [17][18][19][20][21][22][23][24] The enhanced terahertz radiation is maintained over broad bandwidths by the use of nano-antenna sizes much smaller than the terahertz wavelengths. 24 Additionally, using the large device active areas allows efficient operation at high optical pump power levels without being limited by the carrier screening effect and thermal breakdown.…”

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confidence: 99%

High power telecommunication-compatible photoconductive terahertz emitters based on plasmonic nano-antenna arrays

Yardimci

Lü

Jarrahi

2016

Applied Physics Letters

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We present a high-power and broadband photoconductive terahertz emitter operating at telecommunication optical wavelengths, at which compact and high-performance fiber lasers are commercially available. The presented terahertz emitter utilizes an ErAs:InGaAs substrate to achieve high resistivity and short carrier lifetime characteristics required for robust operation at telecommunication optical wavelengths. It also uses a two-dimensional array of plasmonic nano-antennas to offer significantly higher optical-to-terahertz conversion efficiencies compared to the conventional photoconductive emitters, while maintaining broad operation bandwidths. We experimentally demonstrate pulsed terahertz radiation over 0.1-5 THz frequency range with the power levels as high as 300 lW. This is the highest-reported terahertz radiation power from a photoconductive emitter operating at telecommunication optical wavelengths. Published by AIP Publishing. Photoconductive emitters are widely used for generating sub-picosecond pulses in the time-domain terahertz imaging and spectroscopy systems.1-6 Telecommunication wavelengths (e.g., 1550 nm) are one of the most desired regimes for pumping photoconductive emitters due to the availability of high-performance, low-cost and compact fiber lasers. 7,8 However, the performance of previously demonstrated photoconductive terahertz emitters operating at telecommunication wavelengths has been limited by low resistivity of photo-absorbing semiconductor substrates at these wavelengths (e.g., InGaAs). This is because efficient operation of photoconductive terahertz emitters requires accelerating photo-generated carriers by high bias electric fields, which results in high dark currents and thermal breakdown when using low resistivity substrates.Various different techniques have been proposed to overcome the low resistivity limitation of photo-absorbing substrates at telecommunication wavelengths.9-12 One of the most promising solutions is the use of a superlattice of monolayers of ErAs in an InGaAs substrate. Since the ErAs layers act as deep recombination centers inside the superlattice, the resistivity and carrier lifetime of such superlattice structures can be controlled by the number and thickness of ErAs layers. [13][14][15][16] Although the high resistivity and short carrier lifetime characteristics of ErAs:InGaAs substrates can enable a more reliable device operation at telecommunication wavelengths, the radiation power of previously demonstrated ErAs:InGaAs photoconductive terahertz emitters operating at 1550 nm pump wavelengths has been limited by low quantum efficiency of conventional ultrafast photoconductors.In this work, we present a large-area photoconductive terahertz emitter based on a two-dimensional array of plasmonic nano-antennas fabricated on an ErAs:InGaAs substrate. The use of plasmonic nano-antennas allows absorption and concentration of the majority of incident pump photons in close proximity to the nano-antennas. As a result, most of the photo-generated carriers drift to t...

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High power telecommunication-compatible photoconductive terahertz emitters based on plasmonic nano-antenna arrays

Yardimci

Lü

Jarrahi

2016

Applied Physics Letters

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“…Recent experimental attempts have been made to improve the optical-to-THz conversion efficiency of the biased plasmonic based emitters. A plasmonic photomixer biased at 4 V have shown to radiate 1.3 mW power at 0.44 THz with efficiency of 1.3 [10,11]. A planar terahertz antenna integrated into a tip-to-tip nano-gap active region, biased at 15 V, was demonstrated to radiate 100 μW power with efficiency of 0.1% at 0.35 THz [12].…”

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Nanoslit cavity plasmonic modes and built-in fields enhance the CW THz radiation in an unbiased antennaless photomixers array

2016

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A new generation unbiased antennaless CW terahertz (THz) photomixer emitters array made of asymmetric metal-semiconductor-metal (MSM) gratings with a subwavelength pitch, operating in the optical near-field regime, is proposed. We take advantage of size effects in near-field optics and electrostatics to demonstrate the possibility of enhancing the THz power by 4 orders of magnitude, compared to a similar unbiased antennaless array of the same size that operates in the far-field regime. We show that, with the appropriate choice of grating parameters in such THz sources, the first plasmonic resonant cavity mode in the nanoslit between two adjacent MSMs can enhance the optical near-field absorption and, hence, the generation of photocarriers under the slit in the active medium. These photocarriers, on the other hand, are accelerated by the large built-in electric field sustained under the nanoslits by two dissimilar Schottky barriers to create the desired large THz power that is mainly radiated downward. The proposed structure can be tuned in a broadband frequency range of 0.1-3 THz, with output power increasing with frequency.

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“…Mode-beating of light from dual cascaded Distributed Feedback Lasers (DFBs) integrated with a phase section have also been designed to generate THz waves 9 , and a continuous tuning range from 0.3 THz to over 1.34 THz was demonstrated. Recently, a tuning range covering 0.15–3 THz has been realized using a two-section digital DFB laser diode 10 . Though these approaches allow tuning over a broad THz spectrum, extra modulators will be needed for signal encoding in communication applications, which will increase cost and complexity.…”

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Fully integrated multi-optoelectronic synthesizer for THz pumping source in wireless communications with rich backup redundancy and wide tuning range

Hou

Deng

et al. 2016

Sci Rep

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We report a monolithic photonic integrated circuit (PIC) for THz communication applications. The PIC generates up to 4 optical frequency lines which can be mixed in a separate device to generate THz radiation, and each of the optical lines can be modulated individually to encode data. Physically, the PIC comprises an array of wavelength tunable distributed feedback lasers each with its own electro-absorption modulator. The lasers are designed with a long cavity to operate with a narrow linewidth, typically <4 MHz. The light from the lasers is coupled via an multimode interference (MMI) coupler into a semiconductor optical amplifier (SOA). By appropriate selection and biasing of pairs of lasers, the optical beat signal can be tuned continuously over the range from 0.254 THz to 2.723 THz. The EAM of each channel enables signal leveling balanced between the lasers and realizing data encoding, currently at data rates up to 6.5 Gb/s. The PIC is fabricated using regrowth-free techniques, making it economic for volume applications, such for use in data centers. The PIC also has a degree of redundancy, making it suitable for applications, such as inter-satellite communications, where high reliability is mandatory.

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Tunable terahertz wave generation through a bimodal laser diode and plasmonic photomixer

Cited by 48 publications

References 33 publications

High power telecommunication-compatible photoconductive terahertz emitters based on plasmonic nano-antenna arrays

High power telecommunication-compatible photoconductive terahertz emitters based on plasmonic nano-antenna arrays

Nanoslit cavity plasmonic modes and built-in fields enhance the CW THz radiation in an unbiased antennaless photomixers array

Fully integrated multi-optoelectronic synthesizer for THz pumping source in wireless communications with rich backup redundancy and wide tuning range

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