Polarization Bistable Vertical-cavity Surface-emitting Laser Research Articles

Amplification of an Autodyne Signal in a Bistable Vertical-Cavity Surface-Emitting Laser with the Use of a Vibrational Resonance

For the first time, it is demonstrated experimentally that a vibrational resonance in a polarization-bistable vertical-cavity surface-emitting laser can be used to increase the laser response in autodyne detection of microvibrations from reflecting surfaces. In this case, more than 25-fold signal amplification is achieved. The influence of the asymmetry of the bistable potential on the microvibration-detection efficiency is studied.

Усиление автодинного сигнала в бистабильном вертикально-излучающем лазере с использованием вибрационного резонанса

AbstractFor the first time, it is demonstrated experimentally that a vibrational resonance in a polarization-bistable vertical-cavity surface-emitting laser can be used to increase the laser response in autodyne detection of microvibrations from reflecting surfaces. In this case, more than 25-fold signal amplification is achieved. The influence of the asymmetry of the bistable potential on the microvibration-detection efficiency is studied.

All-Optical Shift Register Using Polarization Bistable VCSEL Array

We investigated all-optical shift register operations using 1.55-μm polarization bistable vertical-cavity surface-emitting lasers (VCSELs) formed in an array. The VCSEL array consisted of VCSELs that oscillated with single longitudinal and transverse modes at room temperature. The lasing wavelengths were tuned by adjusting the driving currents of each VCSEL. A VCSEL in the array exhibited polarization flip-flop operation by injection of the orthogonally polarized set-reset input pulses. By injection of the VCSEL output light into another VCSEL in the same array through a polarizer and an optical gate, the second VCSEL also exhibited polarization flip-flop operation according to the polarization state of the first VCSEL. The shift register operation has been successfully demonstrated using two adjacent VCSELs in the array. The optical power needed for polarization switching is usually lower than the VCSEL output power. Thus, this shift register operation was achieved without optical amplifiers.

Polarization-dependent coupling between a polarization-independent high-index-contrast subwavelength grating and waveguides

We investigated the optical coupling between a polarization-independent high-index-contrast subwavelength grating (HCG) and two orthogonal in-plane waveguides. We fabricated the HCG with waveguides on a silicon-on-insulator substrate and demonstrated that a waveguide with a strong output is switched by changing the polarization of light injected into the HCG. The light coupled more strongly to the waveguide in the direction perpendicular to the polarization of the incident light than to that in the parallel direction. If this waveguide-coupled HCG is incorporated into a polarization bistable vertical-cavity surface-emitting laser (VCSEL), the output waveguide can be switched by changing the lasing polarization of the VCSEL.

All-optical 2-bit header recognition and packet switching using polarization bistable VCSELs.

We propose and evaluate an all-optical 2-bit header recognition and packet switching method using two 1.55-µm polarization bistable vertical-cavity surface-emitting lasers (VCSELs) and three optical switches. Polarization bistable VCSELs acted as flip-flop devices by using AND-gate operations of the header and set pulses, together with the reset pulses. Optical packets including 40-Gb/s non-return-to-zero pseudo-random bit-sequence payloads were successfully sent to one of four ports according to the state of two bits in the headers with a 4-bit 500-Mb/s return-to-zero format. The input pulse powers were 17.2 to 31.8 dB lower than the VCSEL output power. We also examined an extension of this method to multi-bit header recognition and packet switching.

Bit Error Rate Measurements of All-Optical Flip-Flop Operations of a 1.55-μm Polarization Bistable VCSEL

We measured the bit error rate (BER) of all-optical flip-flop operations using a 1.55-μm polarization bistable vertical-cavity surface-emitting laser (VCSEL). Polarization bistable flip-flop operations were obtained by injecting optical set and reset pulses with independently adjusted wavelengths toward the two VCSEL lasing modes, whose polarizations are orthogonal to each other. Acquired waveforms showed clearly opened eyes, and BERs less than 1 × 10−9 were measured up to 1 Gb/s although the optical set and reset pulse power was much lower than the VCSEL output power. We also demonstrated all-optical flip-flop operations by injecting optical set and reset pulses with the same wavelength, which were generated by a single laser diode. In this case, we obtained polarization bistable flip-flop operations up to 500 Mb/s with almost the same BER values that were obtained when the wavelengths of the set and reset pulses were adjusted independently. The optical input pulse powers were higher than for the case using input pulses with two different wavelengths, but still lower than the VCSEL output power.

All-Optical Header Recognition and Packet Switching Using Polarization Bistable VCSEL

We demonstrate an optical header processing system using a 1.55-μm polarization bistable vertical-cavity surface-emitting laser (VCSEL) that operates as an all-optical AND gate and a holding element. Depending on the state of 1 bit in the 4-bit header, the VCSEL held one of two-orthogonal polarization states. The light of the VCSEL output through a polarizer switched and held the output state of an optical switch. This enables the payload to be sent to the destination determined by the header. The characteristics of the polarization bistable VCSEL enable low-power consumption and lower latency operation. The system also has the potential to process multibit optical headers involved in ultrafast optical packets.

All-Optical Flip-Flop Operation at 1-mA Bias Current in Polarization Bistable Vertical-Cavity Surface-Emitting Lasers With an Oxide Confinement Structure

Polarization bistable vertical-cavity surface-emitting lasers (VCSELs) with an oxidation confinement structure were fabricated for low power consumption operation. Threshold current of the VCSEL was reduced to 0.22 mA. The VCSEL operated in a single longitudinal and transverse mode and in one of two orthogonal linear polarization modes. All-optical flip-flop operation based on polarization bistability was achieved at a record low bias current of 1.15 mA, which is about one tenth of our previously developed polarization bistable VCSEL without a current confinement structure.

1-GHz All-Optical Flip-Flop Operation of Conventional Cylindrical-Shaped Single-Mode VCSELs Under Low-Power Optical Injection

All-optical set-reset flip-flop operations of conventional circular cylindrical-shaped 1.55-μm wavelength single-mode vertical-cavity surface-emitting lasers (VCSELs) have been demonstrated at a switching frequency of 1 GHz based on polarization bistability observed via injection current variation. The energy of set and reset pulses was lower than 4.5 fJ at a bias current of the VCSEL of 4 mA. Polarization bistable VCSELs will be useful for high-speed optical signal processing applications.

High Switching-Speed Operation of Optical Memory Based on Polarization Bistable Vertical-Cavity Surface-Emitting Laser

Operation conditions of all-optical buffer memories based on polarization bistable vertical-cavity surface-emitting lasers (VCSELs) were investigated. The switching power dependence on the frequency detuning of the input optical signal was measured for a 980-nm polarization bistable VCSEL. The proper operating conditions for 10-Gb/s memory operation were also measured and found to be on the negative detuning side. Calculations based on a two-mode rate-equation model successfully explained the measured characteristics of the switching power dependence on the frequency detuning and the operating conditions. Maximum data rates for the memory operation strongly depended on the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> factor (i.e., photon lifetime) of the VCSELs. A possibility of 40-Gb/s memory operation using a polarization bistable VCSEL with a <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> factor as low as 500 was shown.

All-optical memory operation of 980-nm polarization bistable VCSEL for 20-Gb/s PRBS RZ and 40-Gb/s NRZ data signals

The fastest known operation of all-optical flip-flop memory was experimentally demonstrated using a 980-nm polarization bistable vertical-cavity surface-emitting laser (VCSEL). Operating conditions of the input signal power and the frequency detuning to achieve the fast optical memory operation were characterized experimentally. At the optimum condition, 1-bit data signals were arbitrarily sampled and memorized from a 2(6)-1 pseudorandom bit sequence return-to-zero signal at 20 Gb/s by using AND gate and memory functionalities obtained from the polarization bistability. In addition, 1-bit memory operation was achieved for a 6-bit non-return-to-zero signal at 40 Gb/s. Both memory operations required 250-microW data signal power and had optical gain. The high potential of all-optical flip-flop memories based on polarization bistable VCSELs for use in ultrafast all-optical future networks was demonstrated.

Experimental Demonstration of Multi-Bit Optical Buffer Memory Using 1.55-$\mu{\hbox {m}}$ Polarization Bistable Vertical-Cavity Surface-Emitting Lasers

We demonstrate a novel all-optical buffer memory using 1.55-μm polarization bistable vertical-cavity surface-emitting lasers (VCSELs). A one-bit data is stored as one of two orthogonal polarization states of a VCSEL in this memory. The polarization state is transferred from the VCSEL to another VCSEL which is optically connected in cascade as a shift register. A 4-bit optical buffer memory is constructed using two sets of the shift-register memory connected in parallel. These results show the technical feasibility of multi-bit optical buffer memory.

Polarization-bistable vertical-cavity surface-emitting lasers: application for optical bit memory

AbstractWe summarize recent results on polarization-bistable vertical-cavity surface-emitting lasers (VCSELs) and their application to optical buffer memory. All-optical flip-flop operation with very low switching energies and high repetition rates is achieved. An optical buffer memory consisting of a two-dimensional array of polarization-bistable VCSELs, in which the bit state of the optical signal, “0” or “1”, is stored as a lasing linear polarization state of 0 or 90°. Input data stored as the polarization states of the first VCSEL are transferred to the polarization states of the second VCSEL. In our experiments with 980 nm polarization-bistable VCSELs, 10 Gbit/s optical buffering, 2-bit optical buffering, and a shift register function have been successfully demonstrated.

10-Gb/s Optical Buffer Memory Using a Polarization Bistable VCSEL

Optical buffer memory for 10-Gb/s data signal is demonstrated experimentally using a polarization bistable vertical-cavity surface-emitting laser (VCSEL). The optical buffer memory is based on an optical AND gate function and the polarization bistability of the VCSEL. Fast AND gate operation responsive to 50-ps-width optical pulses is achieved experimentally by increasing the detuning frequency between an injection light into the VCSEL and a lasing light from the VCSEL. A specified bit is extracted from the 10-Gb/s data signal by the fast AND gate operation and is stored as the polarization state of the VCSEL by the polarization bistability. The corresponding numerical simulations are also performed using two-mode rate equations taking into account the detuning frequency. The simulation results confirm the fast AND gate operation by increasing the detuning frequency as well as the experimental results.

Timing Jitter Reduction by All-Optical Signal Regeneration Using a Polarization Bistable VCSEL

All-optical signal regeneration is experimentally demonstrated using a polarization bistable vertical-cavity surface-emitting laser. The retiming operation of signal regeneration is performed by using an AND gate operation and a reset operation. An optical clock pulse and input data signal are used for the AND gate operation. The timing jitter of the regenerated signal is reduced by optimizing the injection power ratio of the clock pulse and the data signal. The retiming operation is analyzed using a simple model that includes random fluctuation of the polarization switching threshold and bandwidth limitation of the response to the injection light.

Low-switching-energy and high-repetition-frequency all-optical flip-flop operations of a polarization bistable vertical-cavity surface-emitting laser

Subfemtojoule polarization bistable switching in a vertical-cavity surface-emitting laser (VCSEL) is experimentally demonstrated. All-optical flip-flop operation of the VCSEL was performed using two orthogonally polarized injection light pulses. The optimum wavelengths of the two injection pulses for achieving minimum switching power were different and corresponded to the lasing wavelengths of the two polarization states of the laser. The pulse width/switching frequency dependence of the injection pulses showed that a minimum switching energy was obtained at 1ns∕500MHz. A record low switching energy of 0.3fJ has been achieved as well as a record high switching frequency of 10GHz.

Optical-injection-induced polarization switching in polarization-bistable vertical-cavity surface-emitting lasers

We present a simple quasianalytical formalism for static polarization-resolved light-current characteristics of dual polarization mode vertical-cavity surface-emitting lasers (VCSELs) under optical injection. Dynamics of optical-injection-induced polarization switching are analyzed and simple analytical estimates for the polarization switching time obtained in particular cases. The results suggest the possibility of ultrafast polarization switching, implying that optical-injection-induced polarization switching in VCSELs can operate as a fast flip-flop operation.