Control Pulse Energy Research Articles

Design and Analysis of X-OR Gate and 4-Bit Binary to 4-Bit Gray and Gray to Binary Code Converter Using Dual Control Dual SOA TOAD (DCDS-TOAD)

Background: In this paper we have design and analyzed 4-bit binary to 4-bit gray code and 4-bit gray to 4-bit gray code converter using dual control dual semiconductor optical amplifier terahertz optical asymmetric demultiplexer (DCDS-TOAD). We used control pulse as a Soliton pulse train. We calculate the extinction ratio, contrast ratio and Q value and found very high values. The high values of E.R., C.R. and Q value distinguishes the high (‘1’) level to the low(‘0’) very clearly also shown the variation of E.R., C.R. and Q value with control pulse energy and amplified spontaneous emission power factor. Methods: The basic equations governing the TOAD performance is simulated using MATLAB. The extinction ratio, contrast ratio and Q value are calculated for analysis of the device. Results: Results of operation for the code converters are performed at a bit rate of 100Gbps. The structure of DCDSTOAD enable us to achieve high values of ER(~ 81dB), CR(~83dB) and Q factor (86dB). A high Q factor shows very low bit error rate (BER). The eye diagram shows a large eye opening (REOP~98.5%). Conclusion: Design and analyzed 4-bit binary to 4-bit gray code and 4-bit gray to 4-bit gray code converter using dual control dual semiconductor optical amplifier terahertz optical asymmetric demultiplexer (DCDS-TOAD) is proposed and analyzed. We used control pulse as a Soliton pulse train. The proposed X-OR gate finds applications in many devices.

Design and analysis of all- optical dual control dual SOA Tera Hertz asymmetric demultiplexer based half adder

Semiconductor Optical Amplifier based half adder in dual control configuration in a nonlinear optical loop mirror is proposed in this communication at 100 Gbps rate. The device is analyzed numerically and Extinction Ratio (ER ~ 81 dB), Contrast Ratio (CR ~ 82 dB), Q value (Q ~ 85 dB) are calculated and their dependence on control pulse energy and spontaneous noise factor is studied. Large relative eye opening of the order of 99.52% for SUM and 95.23% for CARRY output respectively ensure practical feasibility of this device. Almost negligible bit error rate and power penalty make this device suitable for all optical communication systems.

A novel approach to all-optical universal soliton logic gate NAND utilizing reflective semiconductor optical amplifiers

Reflective semiconductor optical amplifier (RSOA) is a versatile gain medium due to its double-pass characteristics compared to ordinary semiconductor optical amplifier. RSOA-based gain dynamics is utilized to design and analyze the NAND gate using soliton pulses for the first time. The simulation results shows that RSOA is a very good candidate for intensity encoded logic gates and processors. Extinction ratio, contrast ratio, amplitude modulation, bit error rate, and eye opening are calculated. Dependence of these performance indication parameters on control pulse energy is also investigated considering amplified spontaneous emission noise. This NAND gate can be used to design any optical logic processors in future, as it is a universal one.

Design and performance analysis of all optical 4-bit parity generator and checker using dual-control dual SOA terahertz optical asymmetric demultiplexer (DCDS-TOAD)

Abstract Tera hertz optical asymmetric demultiplexer (TOAD) using two semiconductor optical amplifiers and two control signals has been used to design an all optical parity checker and generator. The same circuit can generate and check both even and odd parity using a control input. The numerical simulation using Matlab 2007b is done for performance analysis of the proposed device in terms of output bit pattern, amplified spontaneous emission (ASE) noise, extinction ratio, contrast ratio, pseudo eye diagram, relative eye opening (98.9% for 20 dB gain and 96.21% for 10 dB gain) and their variation with input control pulse energy, amplified spontaneous emission noise factor for different unsaturated gain. The simulated value of E.R. = 81.39 dB, C.R. = 83.15 dB, REOP = 98.9% and Q value = 86.16 dB are found for this proposal.

An alternative method for implementation of frequency-encoded logic gates using a terahertz optical asymmetric demultiplexer (TOAD)

All-optical frequency-encoded AND, OR, and NOT logic gates are proposed and their performance simulated to confirm their feasibility. Terahertz optical asymmetric demultiplexer (TOAD)-based logic gates with a control pulse energy as low as 50 fJ are used, and real-time simulations of their input and output pulse patterns reveal a rate of 20 Gbps. Such logic gates could be used for future all-optical logic processors for optical computation and communication systems.

Ultrafast, all-optical control of modal phases in a few-mode fiber for all-optical switching.

The phase differences between the transverse modes of an optical fiber can be altered all-optically by intermodal cross-phase modulation. In this Letter, we experimentally demonstrate this effect with ultrashort laser pulses. An ultrashort probe pulse, guided in both modes of a two-mode fiber, is co-propagating and temporally overlapping with an ultrashort control pulse, guided in the fundamental mode only and centered at a separate wavelength. The use of ultrashort pulses allows for a notable phase shift at a 33-fold reduced control pulse energy and a 173-fold reduced fiber length, compared to previous experiments. A total phase shift of 0.285π between the two probe modes was achieved at a 9 nJ control pulse energy in a 19 cm long two-mode graded-index fiber. Additionally, the capability of this scheme to switch ultrashort pulses in an all-optical manner was investigated. A modulation depth of 50% was achieved, limited by temporal nonlinear effects.

Cavity-Enhanced Room-Temperature Broadband Raman Memory

Broadband quantum memories hold great promise as multiplexing elements in future photonic quantum information protocols. Alkali-vapor Raman memories combine high-bandwidth storage, on-demand readout, and operation at room temperature without collisional fluorescence noise. However, previous implementations have required large control pulse energies and have suffered from four-wave-mixing noise. Here, we present a Raman memory where the storage interaction is enhanced by a low-finesse birefringent cavity tuned into simultaneous resonance with the signal and control fields, dramatically reducing the energy required to drive the memory. By engineering antiresonance for the anti-Stokes field, we also suppress the four-wave-mixing noise and report the lowest unconditional noise floor yet achieved in a Raman-type warm vapor memory, (15±2)×10^{-3} photons per pulse, with a total efficiency of (9.5±0.5)%.

All-Optical 3:8 Decoder with the Help of Terahertz Optical Asymmetric Demultiplexer

An all-optical 3:8 decoder unit with the help of terahertz optical asymmetric demultiplexer (TOAD) is proposed. The all-optical 3:8 decoder unit with a set of all-optical full-adders and optical exclusive-ORs (XORs), can be used to perform a fast central processor unit using optical hardware components. We try to exploit the advantages of TOAD-based optical switch to design an integrated all-optical circuit which can perform decoding of signal. A theoretical model is presented and verified through numerical simulation. The new method promises both higher processing speed and accuracy. The model can be extended for studying more complex all-optical circuit of enhanced functionality in which decoder is the basic building block. The operation of the proposed circuit is parallel in nature. The impact of the switching energy with small signal gain and variation of extinction ratio and contrast ration with control pulse energy of the switching outcome is explored and assessed by means of numerical simulations.

Ultrafast two-color all-optical transverse mode conversion in a graded-index fiber.

We report on experimental conversion of picosecond probe pulses from the fundamental mode (LP01) to the next higher-order mode (LP11) by optically induced transient long-period gratings in a graded-index fiber using subpicosecond control pulses. In contrast to former experiments, the temporally synchronized control (1030 nm) and probe pulses (1250 nm) were easily distinguishable by their wavelengths, allowing for the first direct observation of such an ultrafast transverse mode conversion. Despite a nonperfect pulse duration ratio between control and probe pulses as well as an unavoidable excitation of unwanted higher-order modes, a clear energy conversion of 18% between the LP01-mode and the LP11-mode was observed at 2.3 times lower control pulse energies compared to previous experiments.

Ultrafast, low-power, all-optical switching via birefringent phase-matched transverse mode conversion in integrated waveguides

We demonstrate the potential of birefringence-based, all-optical, ultrafast conversion between the transverse modes in integrated optical waveguides by modelling the conversion process by numerically solving the multi-mode coupled nonlinear Schroedinger equations. The observed conversion is induced by a control beam and due to the Kerr effect, resulting in a transient index grating which coherently scatters probe light from one transverse waveguide mode into another. We introduce birefringent phase matching to enable efficient all-optically induced mode conversion at different wavelengths of the control and probe beam. It is shown that tailoring the waveguide geometry can be exploited to explicitly minimize intermodal group delay as well as to maximize the nonlinear coefficient, under the constraint of a phase matching condition. The waveguide geometries investigated here, allow for mode conversion with over two orders of magnitude reduced control pulse energy compared to previous schemes and thereby promise nonlinear mode switching exceeding efficiencies of 90% at switching energies below 1 nJ.

All-optical half-adder/half-subtractor using terahertz optical asymmetric demultiplexer.

Logic gates are the fundamental building blocks of digital systems. Using these logic gates, one can perform different logic and arithmetic operations. All-optical logic and arithmetic operations are very much expected in high-speed communication systems. In this paper, we present a model to perform addition/subtraction operations on two binary digits based on a terahertz optical asymmetric demultiplexer (TOAD). Using four TOAD-based switches, we have designed a half-adder and half-subtractor circuit. The approach to designing all-optical arithmetic circuits not only enhances the computational speed but is also capable of synthesizing light as inputs to produce the desired outputs. The main advantages of this circuit are that synchronization between inputs is eliminated and simultaneous addition and subtraction operations are realized at the outputs. This circuit is designed theoretically and verified through numerical simulations. The impact of the control pulse energy, gain recovery time, and the input data pulse width on the extinction ratio, contrast ratio, amplitude modulation, Q-factor, and relative opening of the pseudo-eye diagram of the switching outcome is explored and assessed by means of numerical simulations.

All-optical parallel data and address recovery scheme

In this paper, we have presented a parallel system model to recover data and address based on terahertz optical asymmetric demultiplexer (TOAD)/semiconductor optical amplifier (SOA)-assisted Sagnac gate. The architecture is based on a system which has its input information containing data and address. Here, we first convert the original data into a coded form with the help of input address. Then the coded information is transmitted through the optical routing channel. At the receiver end, the model simultaneously extracts data and address at any point of the routing channel. The operations of the circuits are studied theoretically and analyzed through numerical simulations. The variation of contrast ratio, amplitude modulation, extinction ratio and bit error rate with control pulse energy and switching crosstalk with gain ratio has been thoroughly investigated.

All-optical switching in silicon-on-insulator photonic wire nano-cavities

We report on experimental demonstration of all-optical switching in a silicon-on-insulator photonic wire nanocavity operating at telecom wavelengths. The switching is performed with a control pulse energy as low as approximately 0.1 pJ on a cavity device that presents very high signal transmission, an ultra-high quality-factor, almost diffraction-limited modal volume and a footprint of only 5 microm(2). High-speed modulation of the cavity mode is achieved by means of optical injection of free carriers using a nanosecond pulsed laser. Experimental results are interpreted by means of finite-difference time-domain simulations. The possibility of using this device as a logic gate is also demonstrated.

Ultrafast, atto-Joule switch using fiber-optic parametric amplifier operated in saturation

All-optical manipulation of signals carried by lightwaves is attractive because controlling the light directly can be more efficient, allows a multitude of signal formats, and can also prove most cost effective. We implemented a novel scheme for ultrafast optical switching using very small control energy that relies on the use of a saturated fiber-optic parametric amplifier. Approximately 19 aJ (150 photons) of control pulse energy was needed for 50% extinction of the signal which is three to four orders of magnitude smaller than in other all-optical switching demonstrations. This allows the consideration of novel practical approaches to implement all-optical switching devices and all-optical subsystems for telecommunications and other applications.

Ultrafast, atto-Joule switch using fiber-optic parametric amplifier operated in saturation

All-optical manipulation of signals carried by lightwaves is attractive because controlling the light directly can be more efficient, allows a multitude of signal formats, and can also prove most cost effective. We implemented a novel scheme for ultrafast optical switching using very small control energy that relies on the use of a saturated fiber-optic parametric amplifier. Approximately 19 aJ (150 photons) of control pulse energy was needed for 50% extinction of the signal which is three to four orders of magnitude smaller than in other all-optical switching demonstrations. This allows the consideration of novel practical approaches to implement all-optical switching devices and all-optical subsystems for telecommunications and other applications.

All-optical demultiplexing of 160–10Gbit∕s signals with Mach-Zehnder interferometric switch utilizing intersubband transition in InGaAs∕AlAs∕AlAsSb quantum well

We have developed a Mach-Zehnder interferometric all-optical switch employing intersubband transition in an InGaAs∕AlAs∕AlAsSb-coupled double quantum well waveguide. The recently discovered cross-phase modulation phenomenon was utilized as the switching mechanism; the nonlinear index of refraction for transverse electric polarized light is induced by intersubband optical excitation using transverse magnetic pump light. We demonstrate the demultiplexing operation of 160Gbit∕s data signals to 10Gbit∕s using this switch. At the input control pulse energy of 8pJ, the demultiplexed signals showed an extinction ratio better than 10dB, and an error-free demultiplexing was achieved.

Absorption Dynamics in All-Optical Switch Based on Intersubband Transition in InGaAs–AlAs–AlAsSb Coupled Quantum Wells

We developed a pigtailed fiber module including an intersubband transition all-optical switch using InGaAs-AlAs-AlAsSb coupled double quantum wells and studied the absorption saturation dynamics. An increased extinction ratio was obtained by optimizing the delay time between control and signal pulses due to the reduced effect of two-photon absorption. An extinction ratio of 10 dB was obtained for a fiber input pulse energy of 16 pJ (200-fs pulsewidth). The absorption recovery time varied from 600 fs to 2 ps depending on the control pulse energy

Ultrafast all-optical switching with low saturation energy via intersubband transitions in GaN/AlN quantum-well waveguides

A fiber-optic pump-probe setup is used to demonstrate all-optical switching based on intersubband cross-absorption modulation in GaN/AlN quantum-well waveguides, with record low values of the required control pulse energy. In particular, a signal modulation depth of 10 dB is obtained with control pulse energies as small as 38 pJ. Such low power requirements for this class of materials are mainly ascribed to an optimized design of the waveguide structure. At the same time, the intersubband absorption fully recovers from the control-pulse-induced saturation on a picosecond time scale, so that these nonlinear waveguide devices are suitable for all-optical switching at bit rates of several hundred Gb/s.

Intersubband all-optical switching in submicron high-mesa SCH waveguide structure with wide-gap II-VI-based quantum wells

An all-optical switch using intersubband transition in wide-gap II-VI-based quantum wells in an improved waveguide structure is presented. The waveguide exhibits a separate confinement heterostructure (SCH) and submicron high-mesa waveguide for stronger optical confinement. A reduction of 39% is achieved in control pulse energy for a 10 dB switching extinction ratio while maintaining a subpicosecond response.

Polarization dependent loss in III-nitride optical waveguides for telecommunication devices

Excess polarization dependent loss (PDL) was investigated for GaN waveguide devices grown by molecular beam epitaxy (MBE). The loss for transverse magnetic polarization strongly depended on the edge dislocation density in the crystal, because the dislocations capture electrons and act like a wire-grid polarizer. By means of MBE regrowth on GaN grown with metal-organic chemical vapor deposition (MOCVD), the PDL was reduced to 1∼2dB∕mm with an edge dislocation density of 3×109cm−2, whereas it was approximately 10dB∕mm for an all-MBE-grown sample. An ultrafast all-optical switch utilizing the intersubband transition was fabricated with a multiple quantum well structure that was regrown with MBE on MOCVD-grown GaN. An extinction ratio of as high as 11.5dB was achieved with a control pulse energy of 150pJ, which is attributable to the reduction of the excess PDL.