Vertical junction silicon microdisk modulators and switches

Abstract

Vertical junction resonant microdisk modulators and switches have been demonstrated with exceptionally low power consumption, low-voltage operation, high-speed, and compact size. This paper reviews the progress of vertical junction microdisk modulators, provides detailed design data, and compares vertical junction performance to lateral junction performance. The use of a vertical junction maximizes the overlap of the depletion region with the optical mode thereby minimizing both the drive voltage and power consumption of a depletion-mode modulator. Further, the vertical junction enables contact to be made from the interior of the resonator and therein a hard outer wall to be formed that minimizes radiation in small diameter resonators, further reducing the capacitance and drive power of the modulator. Initial simple vertical junction modulators using depletion-mode operation demonstrated the first sub-100 fJ/bit silicon modulators. With more intricate doping schemes and through the use of AC-coupled drive signals, 3.5 μm diameter vertical junction microdisk modulators have recently achieved a communications efficiency of 3 fJ/bit, making these modulators the smallest and lowest power modulators demonstrated to date, in any material system. Additionally, the demonstration was performed at 12.5 Gb/s, required a peak-to-peak signal level of only 1 V, and achieved bit-error-rates below 10(-12) without requiring signal pre-emphasis. As an additional benefit to the use of interior contacts, higher-order active filters can be constructed from multiple vertical-junction modulators without interference of the electrodes. Doing so, we demonstrated second-order active high-speed bandpass switches with ~2.5 ns switching speeds, and power penalties of only 0.4 dB. Through the use of vertical junctions in resonant modulators, we have achieved the lowest power consumption, lowest voltage, and smallest silicon modulators demonstrated to date.

Ge-on-Si photonic devices for photonic-electronic integration on a Si platform

“…An injection of carriers under a forward bias [63] or a depletion of carriers by heavily doping under a reverse bias [62] is used to obtain the modulation of refractive index. Table II summaries the recent reports [65,66,67,68,69,70] on the performance of Si EO modulators [65,66,67,70] together with the performance of Ge-based electro-absorption (EA) modulators [68,69] described below. In Si MZI modulators, the operation speed more than 10 Gbps has been reported with the operation spectrum width over 30 nm [63,65,66,67].…”

“…However, a large energy (> 4 pJ/bit) is consumed for modulations due to the length of devices more than 100 µm [63,65,66]. A reduced size of optical modulator using a Si ring/disk resonator as small as 10 µm in diameter has been reported for the reduction of energy consumption [70,71,72]. The energy can be reduced to be on the order of 0.1 pJ/bit or below, which is smaller by more than one order of magnitude in comparison with the MZI devices.…”

High-Speed, Low Drive-Voltage Silicon-Organic Hybrid Modulator Based on a Binary-Chromophore Electro-Optic Material

“…In contrast, carrier-depletion modulators support symbol rates of up to 50 GBd [4], but typical voltage-length products are beyond 10 Vmm [5], [6] and thus much larger than those of injection-type devices. Drive voltage and device footprint can be strongly reduced by using resonant structures [5], [7]. However, resonant devices feature limited optical bandwidth and their resonance wavelength is particularly prone to temperature fluctuations Silicon-organic hybrid (SOH) integration pursues a fundamentally different approach [8], [9].…”

High-Speed Silicon-Organic Hybrid (SOH) Modulator with 1.6 fJ/bit and 180 pm/V In-Device Nonlinearity

“…Modulation energies can be significantly reduced by using resonant structures, such as ring resonators, microdisks or photonic crystal waveguides. The lowest energy consumption reported to date for a silicon-based modulator amounts to 3 fJ/bit and has been achieved with a microdisk modulator operated at a data rate of 12.5 Gbit/s with a drive voltage of 1 V pp and an ER of 3.2 dB [7]. However, both carrier injection and depletion type modulators are subject to an inherent coupling of amplitude and phase modulation, and resonant structures suffer from strong wavelength dependence and temperature sensitivity.…”