Optical modulation at around 1550 nm in an InGaAlAs optical waveguide containing an InGaAs/AlAs resonant tunneling diode

Abstract

We report electroabsorption modulation of light at around 1550 nm in a unipolar InGaAlAs optical waveguide containing an InGaAs/AlAs double-barrier resonant tunneling diode ͑RTD͒. The RTD peak-to-valley transition increases the electric field across the waveguide, which shifts the core material absorption band edge to longer wavelengths via the Franz-Keldysh effect, thus changing the light-guiding characteristics of the waveguide. Low-frequency characterization of a device shows modulation up to 28 dB at 1565 nm. When dc biased close to the negative differential conductance region, the RTD optical waveguide behaves as an electroabsorption modulator integrated with a wide bandwidth electrical amplifier, offering a potential advantage over conventional pn modulators. © 1999 American Institute of Physics. ͓S0003-6951͑99͒00748-2͔Because of their intrinsic high-speed response and potential for electrical gain over a wide bandwidth, resonant tunneling diodes ͑RTDs͒ have been proposed by several groups 1-3 for optoelectronic applications. Previously, we reported work on an GaAs/AlAs RTD that was successfully integrated in a unipolar GaAs-AlGaAs optical waveguide, 4 and high-speed optical modulation ͑up to 18 dB͒ combined with electrical gain was demonstrated. 5 This device operated around 900 nm. For devices functioning at the usual optical communication wavelengths, 1300 or 1550 nm, applications could include, for example, optical distribution of modulated millimeter-wave frequency carriers for mobile communication systems. In this letter we describe a resonant tunneling diode electroabsorption modulator ͑RTD-EAM͒ operating at wavelengths around 1550 nm.The operation of the device is based on a RTD within an optical waveguide which introduces a nonuniform electric field distribution across the waveguide core. The electric field becomes strongly dependent on the bias voltage, due to accumulation and depletion of electrons in the emitter and collector sides of the RTD, respectively. Depending on the dc bias operating point, a small high frequency ac signal ͑Ͻ1 V͒ can induce high-speed switching. This produces substantial high-speed modulation of the waveguide optical absorption coefficient at a given wavelength near the material band edge via the Franz-Keldysh effect 4 and, therefore, modulates light at photon energies lower than the waveguide core band-gap energy. The modulation depth can be considerable because, under certain conditions, the RTD operation point switches well into the two positive differential resistance portions of the current-voltage ͑I-V͒ characteristic, with a substantial part of the terminal voltage dropped across the depleted region in the collector side. 5,6 The advantage of the RTD-EAM compared to conventional pn modulators is that, when dc biased close to the negative differential conductance ͑NDC͒ region, the device behaves as an optical waveguide electroabsorption modulator integrated with a wide bandwidth electrical amplifier.The high-frequency and large modulation depth characteristics of ...

Ultralow voltage resonant tunnelling diode electroabsorption modulator

“…In summary, devices with 4×200 µm 2 active area showing the highest peak-to-valley current (PVCR) and largest peak-to-valley voltage swing ∆V p-v , when dc biased to the optimum operating point, had a maximum modulation depth of 28 dB at around 1565 nm [11]; typical 4×200 µm 2 active area devices showed a modulation depth of around 20 dB in the wavelength range 1560-1567 nm, with propagation loss in the transmissive state estimated to be ~5 dB [13].…”

“…Simpler optoelectronic device structures essentially based on double barrier resonant tunnelling diode (DBRTDs) have also been used in various applications; these include photodetectors at optical communication wavelengths [7], mid-infrared wavelengths [8] and, optical modulators [9][10] [11].…”

Electric field switching in a resonant tunneling diode electroabsorption modulator

“…Preliminar electroabsorption modulation results have been previously reported [10]; in summary, devices with 4 × 200 µm 2 active area showing the highest PVCR and largest ∆V v−p , when dc biased to the optimum operating point, had a maximum modulation depth of 28 dB at around 1565 nm [10]. vices showed a modulation depth of around 20 dB in the wavelength range 1560-1567 nm, with propagation loss in the transmissive state estimated to be ∼5 dB [14].…”

“…Simpler optoelectronic device structures essentially based on double barrier resonant tunneling diodes (DBRTD) have also been used in various applications; these include photodetectors at optical communication wavelengths [6], midinfrared wavelengths [7] and, closely related to the work presented here, optical modulators [8][9] [10].…”

Resonant Tunneling Diode Optoelectronic Circuits Applications in Radio-Over-Fiber Networks

“…The epitaxial structure includes InGaAlAs layers that in previous study [14] helped to implement RTD devices as electro-absorption modulators and waveguide photo-detectors (PDs). In this study, the RTDs have been processed as pillars where the InGaAlAs layers are used to improve the absorption of light at a wavelength of 1550 nm.…”