An all-silicon passive optical diode.
ABSTRACT A passive optical diode effect would be useful for on-chip optical information processing but has been difficult to achieve. Using a method based on optical nonlinearity, we demonstrate a forward-backward transmission ratio of up to 28 decibels within telecommunication wavelengths. Our device, which uses two silicon rings 5 micrometers in radius, is passive yet maintains optical nonreciprocity for a broad range of input power levels, and it performs equally well even if the backward input power is higher than the forward input. The silicon optical diode is ultracompact and is compatible with current complementary metal-oxide semiconductor processing.
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ABSTRACT: One-way optical transmission through a composite structure of grating-photonic crystal (PC) is presented. This unidirectional transportation property originates from the diffraction of grating to change the direction of light incident into the PC from pseudobandgaps to passbands of the PC. Numerical simulation shows that a light beam in a certain range of frequencies can transmit the composite structure when it is incident from the grating interface but is completely reflected by the structure when it is incident from the PC interface, which is further verified experimentally. The present structure may provide another more compact way for designing on-chip optical diode-like integrated devices.Optics Letters 08/2014; 39(16). · 3.39 Impact Factor
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ABSTRACT: This work demonstrates an electrically tunable silicon nitride (SiN) micro-ring resonator with polymer-stabilized blue phase liquid crystals (PSBPLCs) cladding. An external vertical electric field is applied to modulate the refractive index of the PSBPLCs by exploiting its fast-response Kerr effect-induced birefringence. The consequent change in the refractive index of the cladding can vary the effective refractive index of the micro-ring resonator and shift the resonant wavelength. Crystalline structures of PSBPLCs with a scale of the order of hundreds of nanometers ensure that the resonator has a very low optical loss. The measured tuning range is 0.45 nm for TM polarized light under an applied voltage of 150V and the corresponding response time is in the sub-millisecond range with a Q-factor of greater than 20,000.Optics Express 07/2014; 22(15). · 3.53 Impact Factor
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ABSTRACT: We demonstrate the first active optical isolator and circulator implemented in a linear and reciprocal material platform using commercial Mach-Zehnder modulators. In a proof-of-principle experiment based on single-mode polarization-maintaining fibers, we achieve more than 12.5 dB isolation over an unprecedented 8.7 THz bandwidth at telecommunication wavelengths, with only 9.1 dB total insertion loss. Our architecture provides a practical answer to the challenge of non-reciprocal light routing in photonic integrated circuits.Optics Express 06/2014; 22(14). · 3.53 Impact Factor
Supporting Online Material for
An All-Silicon Passive Optical Diode
Li Fan, Jian Wang, Leo T. Varghese, Hao Shen, Ben Niu, Yi Xuan, Andrew M. Weiner,
*To whom correspondence should be addressed. E-mail: firstname.lastname@example.org
Published 22 December 2011 on Science Express
This PDF file includes:
Materials and Methods
Materials and Methods
We fabricated the microrings on a silicon-on-insulator wafer (from SOITEC) with a
250 nm-thick top silicon layer and 3 μm of buried oxide. The single-crystalline Si
microrings and waveguides have a rectangular cross-section of 250 nm in thickness and
500 nm in width, which supports a low-loss single-mode quasi-transverse magnetic (TM)
mode for the filters at near infrared. The device was patterned with high resolution
electron-beam lithography (Vistec VB6) which has a beam step size of 2 nm. The diode
was formed after reactive-ion etching with chlorine/argon gas mixture in an inductive-
coupled plasma tool. No cladding was applied over the silicon waveguides or microrings.
Titanium micro-heaters with 5.3 kΩ resistance were evaporated on top of the buried
dioxide next to only the micro-ring resonator in the NF. Fabricated chip was manually
cleaved and has a width ~5 mm. No polishing or other treatments were applied to the
The key prerequisite for our optical diode is the matching of the resonant
wavelengths of the two high-Q filters when they are operating in linear regime, i.e. with
very low incident power. It is well known that as-fabricated high-Q microrings cannot
match exactly in their resonant wavelengths due to limited precision in nanofabrication.
We targeted the radii of the two microrings in the NF and ADF at 5 μm and 5.002 μm,
respectively. In most cases, this will make the resonant wavelength of the NF slightly
shorter than that of the ADF. A titanium micro-heater was then placed to the side of the
microring in the NF so that we can red-shift the resonant wavelength of the NF to match
that of the ADF, through thermo-optic effect (19) of silicon. Compared to the
conventional way of placing the heater above the microring and cladding, depositing the
heater to the side of the microring reduces the heating efficiency. However, it preserves
the high Q and the thermal isolation of the microrings, which are critical for low-power
Experimental Setup and Measurement Details
A continuous-wave tunable laser source with 1 pm resolution was guided into the
device with the help of single mode tapered lensed fiber and the output was coupled out
using another single mode tapered lensed fiber and fed into an optical power meter. The
fibers were position on xyz nanopositioned stages and butt coupled to the waveguides on
either facets of the device. Even though the fabricated device and method of coupling has
a rather high insertion loss of ~21.4 dB due to the facets, no amplifiers were used since
optical nonreciprocity was achieved at low power. A fiber-based polarization controller
was used to control the polarization of light input into the device to obtain maximum
extinction of the NF. A fiber based variable power optical attenuator was used to control
the amount of optical power fed to the device.
To tune the resonance of the NF to the ADF, the microheater to the side of the NF
was heated using a constant voltage source so that the dip of the NF overlaps the peak of
the ADF. Forward and backward spectra were obtained by switching the input and output
fiber connectors. Two scan modes were used to fetch the spectra: continuous-mode scan
where the laser sweeps from the beginning wavelength to the end wavelength without
stops while the power meter takes a moving average of the received optical power, and
stepped-mode scan where the laser goes to each wavelength and stops while the power
meter averages for a reasonably long time.
For point measurements, the wavelength was fixed at the desired operating
wavelength, which typically is the resonance wavelength of the NF in the backward
direction, and transmitted power was taken 10 seconds after the laser was turned on. The
standard deviation of the nonreciprocal transmission ratio includes contributions from
both the forward and backward transmissions and a Fabry-Perot uncertainty of ±0.4 dB.
Optical diode performance for different laser source power levels at 1630.011 nm.
5 ~270 -49.8 ± 1.5
10 ~850 -51.7 ± 1.5
at the diode
-27.5 ± 1
-24.8 ± 1
22.3 ± 1.8
26.9 ± 1.8
14 ~2,100 -52 ± 1.5 -23.6 ± 1 28.4 ± 1.8
A model based on coupled mode theory (21, 22) was developed to describe the
nonlinear response of the side coupled microring resonator. Nonlinear effects considered
include third order nonlinearity χ(3), such as two-photon absorption(TPA) and Kerr effect;
free carrier effect (FCE); and thermal effect resulted from Joule heating from TPA
process, FCE and linear absorption process. In our case, the thermal effect dominates all
other effects and caused the red-shift of the resonance at elevated temperature. With
various coefficients taken from literature, including an estimated thermal dissipation time
of 2 μs (21-23), as well as effective nonlinearity volumes calculated accurately through
finite-difference time domain (FDTD) simulation (20, 24), we can simulate the nonlinear
responses of the NF and ADF using MATLAB.
References and Notes
1. H. A. Haus, Waves and Fields in Optoelectronics (Prentice-Hall, Englewood Cliffs,
NJ, 1984), pp. 56–61.
2. R. L. Espinola, T. Izuhara, M. C. Tsai, R. M. Osgood Jr., H. Dötsch, Magneto-optical
nonreciprocal phase shift in garnet/silicon-on-insulator waveguides. Opt. Lett. 29,
941 (2004). doi:10.1364/OL.29.000941 Medline
3. T. R. Zaman, X. Guo, R. J. Ram, Faraday rotation in an InP waveguide. Appl. Phys.
Lett. 90, 023514 (2007). doi:10.1063/1.2430931
4. L. Bi et al., On-chip optical isolation in monolithically integrated non-reciprocal
optical resonators. Nat. Photonics 5, 758 (2011). doi:10.1038/nphoton.2011.270
5. S. F. Mingaleev, Y. S. Kivshar, Nonlinear transmission and light localization in
photonic-crystal waveguides. J. Opt. Soc. Am. B 19, 2241 (2002).
6. K. Gallo, G. Assanto, K. R. Parameswaran, M. M. Fejer, All-optical diode in a
periodically poled lithium niobate waveguide. Appl. Phys. Lett. 79, 314 (2001).
7. M. Soljačić, C. Luo, J. D. Joannopoulos, S. Fan, Nonlinear photonic crystal
microdevices for optical integration. Opt. Lett. 28, 637 (2003).
8. A. Rostami, Piecewise linear integrated optical device as an optical isolator using two-
port nonlinear ring resonators. Opt. Laser Technol. 39, 1059 (2007).
9. S. K. Ibrahim, S. Bhandare, D. Sandel, H. Zhang, R. Noe, Non-magnetic 30 dB
integrated optical isolator in III⁄V material. Electron. Lett. 40, 1293 (2004).
10. J. Hwang et al., Electro-tunable optical diode based on photonic bandgap liquid-
crystal heterojunctions. Nat. Mater. 4, 383 (2005). doi:10.1038/nmat1377
11. S. Manipatruni, J. T. Robinson, M. Lipson, Optical nonreciprocity in optomechanical
structures. Phys. Rev. Lett. 102, 213903 (2009).
12. Z. Yu, S. Fan, Complete optical isolation created by indirect interband photonic
transitions. Nat. Photonics 3, 91 (2009). doi:10.1038/nphoton.2008.273
13. M. S. Kang, A. Butsch, P. S. J. Russell, Reconfigurable light-driven opto-acoustic
isolators in photonic crystal fibre. Nat. Photonics 5, 549 (2011).
14. B. E. Little, S. T. Chu, H. A. Haus, J. Foresi, J.-P. Laine, Microring resonator channel
dropping filters. J. Lightwave Technol. 15, 998 (1997). doi:10.1109/50.588673
15. Q. Xu, B. Schmidt, S. Pradhan, M. Lipson, Micrometre-scale silicon electro-optic
modulator. Nature 435, 325 (2005). doi:10.1038/nature03569 Medline
16. S. Xiao, M. H. Khan, H. Shen, M. Qi, Compact silicon microring resonators with
ultra-low propagation loss in the C band. Opt. Express 15, 14467 (2007).