Optimization of efficiency-loss figure of merit in carrier-depletion silicon Mach-Zehnder optical modulator

Abstract

In this paper we study the optimization of interleaved Mach-Zehnder silicon carrier depletion electro-optic modulator. Following the simulation results we demonstrate a phase shifter with the lowest figure of merit (modulation efficiency multiplied by the loss per unit length) 6.7 V-dB. This result was achieved by reducing the junction width to 200 nm along the phase-shifter and optimizing the doping levels of the PN junction for operation in nearly fully depleted mode. The demonstrated low FOM is the result of both low V(π)L of ~0.78 Vcm (at reverse bias of 1V), and low free carrier loss (~6.6 dB/cm for zero bias). Our simulation results indicate that additional improvement in performance may be achieved by further reducing the junction width followed by increasing the doping levels.

Analysis of efficiently poled electro-optic polymer/Tio2 vertical slot waveguide modulators

“…Our hybrid polymer modulator has a V π L e product of 1.56 V cm and a V π Loss product of 7.8 V dB in the hybrid EOP/SG silica waveguide modulator [2]. To the best of the authors' knowledge, one of the best reported Si modulators to date showed a V π L e product of 0.78 V cm and a V π Loss product of 6.7 V dB [4], although other Si modulators showed V π L e products of 1-3 V cm with higher V π Loss products of 427 V dB [5][6][7][8]. Other CMOS compatible modulators include the III-V electro-absorption modulator (EAM) with a bandwidth of 52 GHz [9], EOP/Si slot waveguides, and EOP/Si photonic crystal (PC) waveguide modulators [10][11][12][13][14], and the properties of these devices are summarized in Table 1. EOP/Si slot waveguide modulators were demonstrated based on coplanar Si slot waveguides [11][12][13], in which no optical modes exist in the high-index Si; instead, the waveguide mode was confined within the low index EOP between the Si slots, because the Si size is critically reduced to a less than single mode condition (λ/2n effective ), where λ is the wavelength and n effective is the effective refractive index of the waveguide.…”

“…We have previously demonstrated a low half-wave voltage (V π ) in the 0.65-1.0 V range [2,3] with relatively low optical propagation loss of 5 dB/cm, using a hybrid EOP/sol-gel (SG) silica waveguide modulator with an in-device electro-optic (EO) coefficient of 142 pm/V at a wavelength of 1550 nm. The V π L e product (where V π is the half-wave voltage, and L e is the electrode length) is considered to be an appropriate figure of merit (FOM) for a complementary metal-oxide-semiconductor (CMOS)-compatible integrated optical modulator for optical interconnections based on Si modulators [4][5][6][7][8]. Only a few reports on Si modulators have focused on the optical losses for realistic applications.…”

Silicon-based phase shifters for high figure of merit in optical modulation

“…The configuration is similar to interleaved or interdigitated PN-junction phase shifters in terms of folded PN junction layout. [19][20][21][22][23][24] The serpentine PN-junction presented here is, however, more suitable to higher modulation efficiency than with the conventional interleaved PN junction because lightly doped side area has been formed in N-doped area of the rib core. Formation of serpentine PN-junction shape was confirmed experimentally as microscopy images obtained by means of scanning capacitance microscopy (SCM).…”

Demonstration of a High Extinction Ratio Monolithic CMOS Integrated Nanophotonic Transmitter and 16 Gb/s Optical Link

“…Significant progress has been reported on the design and manufacturing of CMOS compatible Mach-Zehnder modulators (MZMs) [9]- [15], [20]- [39] and reverse biased plasma dispersion electro-optic phase shifters [39]- [48]. However, designing a monolithic TX implies limits on attainable CMOS direct drive voltages according to the capabilities of the technology.…”