Design of hybrid optical waveguide with a 90° bend structure for high density photonics integrated circuits

A hybrid optical waveguide having a 90° sharp bend structure, composed of a dielectric straight waveguide, tapered dielectric strip waveguide, and microscale metal gap waveguide, is proposed and simulated to improve the efficiency of light coupling between dielectric and plasmonic waveguides. Our simulation result is a critical step for the hybrid integration of plasmonic components with conventional dielectric components.     

Stationary-fiber rotary probe with unobstructed 360° view for optical coherence tomography

A side-scanning fiber probe is a critical component for optical coherence tomography in medical imaging and diagnosis. We propose and fabricate an on-axis rotating probe that performs in situ, circumferential scanning that is shadow-free (not susceptible to shadow effects caused by the motor's wires). A miniature motor that incorporates a bored-out shaft for the optical fiber is located at the distal end of the probe, which results in a more stable and uniform circumferential scan, free from wire-shadow interference effects. More importantly, this design, novel to our knowledge, compared to other probes avoids the insertion losses introduced by optical coupling components and the multitude of optical interfaces, which is very important for sensing weak signals backscattered from structures deep in the tissue.     

Robust free space board-to-board optical interconnect with closed loop MEMS tracking

We present a free-space optical interconnect system capable of dynamic closed-loop optical alignment using a microlens scanner with a proportional integral and derivative controller. Electrostatic microlens scanners based on combdrive actuators are designed and characterized with vertical cavity surface emitting lasers (VCSELs) for adaptive optical beam tracking in the midst of mechanical vibration noise. The microlens scanners are fabricated on silicon-on-insulator wafers with a bulk micromachining process using deep reactive ion etching. We demonstrate dynamic optical beam positioning with a 700 Hz bandwidth and a maximum noise reduction of approximately 40 dB. Eye diagrams with a 1 Gb/s modulation rate are presented to demonstrate the improved optical link in the presence of mechanical noise.     

Fabrication and characterization of hollow metal waveguides for optical interconnect applications

As data rates continue to increase in high-performance computer systems and networks, it is becoming more difficult for copper-based interconnects to keep pace. An alternative approach to meet these requirements is to move to optical-based interconnect technologies which offer a number of advantages over the legacy copper-based solutions. In order to meet the stringent requirements of high performance and low cost, manufacturable waveguide technologies must be developed. Past solutions have often employed polymer waveguide technologies, which can be expensive and limited by modal dispersion. In the present work, hollow metal waveguides (HMWGs) are investigated as a potential alternative. These waveguides demonstrate very low optical losses of <0.05 dB/cm and the capability to transmit at extremely high data rates. The fabrication, modeling, characterization of the HMWGs are discussed to enable photonic interconnect solutions for future generations of computer and server products.     

High common mode rejection ratio InP 90° optical hybrid in ultra-broadband at 60 nm with deep-rigded waveguide based on ×4 MMI coupler

An In P optical 90° hybrid based on a ×4 MMI coupler with a deep ridged waveguide is designed and fabricated. The working principle of the 90° hybrid is systematically introduced. Three-dimensional beam ropagation method(3D BPM) is used to optimize the structure parameters of the 90° hybrid. The designed compact structure is demonatrated to have a low excess loss less than -0.15 dB, a high common mode rejection ratio better than 40 d B, and a low relative phase deviation less than ±2.5° . The designed hybrid is manufactured on a sandwitched structure deposited on an In P substrate. The measured results show that the common mode rejection ratios are larger than 20 d B in a range from 1520 nm to 1580 nm.The phase deviations are less than ±5° in a range from 1545 nm to 1560 nm and less than ±7° across the C band. The designed 90° optical hybrid is suitable well for realizing miniaturization, high-properties, and high bandwidth of coherent receiver.     

Performance improvement for optical packet switch with shared buffers

In this paper, an inner wavelength method is proposed to enlarge buffering capacity of shared fiber delay line buffers. In addition, an optical packet switch called extended shared buffer type optical packet switch (extended SB-OPS) is proposed to realize the inner wavelength method. In order to further improve performance of extended SB-OPS, a greedy algorithm based on inner wavelength method is introduced. The performance of extended SB-OPS is evaluated by simulation experiments.     

Solitary wave for a nonintegrable discrete nonlinear Schr?dinger equation in nonlinear optical waveguide arrays

We study a nonintegrable discrete nonlinear Schr?dinger (dNLS) equation with the term of nonlinear nearest-neighbor interaction occurred in nonlinear optical waveguide arrays. By using discrete Fourier transformation, we obtain numerical approximations of stationary and travelling solitary wave solutions of the nonintegrable dNLS equation. The analysis of stability of stationary solitary waves is performed. It is shown that the nonlinear nearest-neighbor interaction term has great influence on the form of solitary wave. The shape of solitary wave is important in the electric field propagating. If we neglect the nonlinear nearest-neighbor interaction term, much important information in the electric field propagating may be missed. Our numerical simulation also demonstrates the difference of chaos phenomenon between the nonintegrable dNLS equation with nonlinear nearest-neighbor interaction and another nonintegrable dNLS equation without the term.     

Piezoelectric film electro-deposition for optical fiber sensor with ZnO coating

The piezoelectric film electro-deposition for optical fiber sensor with ZnO coating is studied.The zinc oxide plating film is made on the copper surface directly by cathodic electro-deposition in the Zn(NO_3)_2 single salt aqueous solution systems.The influences of main experimental conditions on the properties of ZnO thin film in the electro-deposition processes are analyzed and a stable,practical and economic technique is obtained.     

Laser beam characteristic for laser resonators with diffraction optical elements

The matrix eigenvalue method is used to analyze a laser resonator composed of diffraction optical elements. The results show that this type of resonator can separate fundamental mode and high order modes effectively. The output beams can be designed for different requests.     

NOLM-based wavelength conversion with FBG band-pass filter for optical packet switching

Nonlinear-optical-loop-mirror wavelength conversion is studied in details. A set of two-phase-shiftedBragg gratings are introduced into the coverter,serving as a narrow band-pass filter to remove newfrequencies generated by walk-off and to compensate the dispersion. Numerical simulations are performedto validate our method. The results show that the converted pulses after the filter are reshaped and,sometimes, even compressed.     

A novel technique for wireless optical communications with lenslet array processor

A novel communication technique is proposed, which utilizes a set of mutually distinguishable optical patterns instead of convergent facula to transmit information. Then the capacity is increased by exploiting the optical spatial bandwidth resources. At last, we experimentally demonstrate the proposed communication technique based on four 8×8 spatial pattern signals by using lenslet array processor.     

Numerical simulation for characterizing femtosecond optical pulses with the SPIDER algorithm

In this article based on the spectral phase interferometry for direct electric-field reconstruction (SPIDER), the femtosecond pulses with various phase characters are numerically simulated. The spectral phases and amplitudes of the transform-limited pulse, the linear chirped pulse, the cubic dispersion pulse, the quartic dispersion pulse, the self-phase modulation pulse and the pulses with the combination of different chirped characters are retrieved. These characterized pulses are applicable to the real-time measurement as samples for diagnosing the chirped characters of pulses quickly.     

Bit-error rate for free-space optical communication with tip–tilt compensation

In this paper, a new kind of method is developed to analyse the bit-error rate for a free-space optical communication system, which is based on the three most important parameters of scintillation statistics, i.e. fraction of time of fade and surge, mean frequency of level crossings, and mean duration of fade and surge. By using this method, the relationship between the bit-error rate and scintillation is clearly identified. The tip–tilt error deteriorates the performance of a free-space optical communication system. Fine tracking ability of adaptive optics (through tip–tilt compensation) can overcome this difficulty. The fade and surge statistical parameters with tip–tilt compensation are evaluated for the plane wave model. The bit-error rate as a function of the scintillation statistical parameters (with tip–tilt compensation) is developed. The results show that the bit-error rate is reduced notably through tip–tilt compensation for free-space optical communication.     

Miniaturized 90° light path conversion device fabricated from UV-curable resin for optical interconnection

A new 90° light path conversion device incorporating a core element and a hybrid comb-clad that combines air and polymer components is proposed for optical interconnection. The device has a large refractive index difference (Δn) between the core and the hybrid comb-clad, which enables a small curvature radius. Extension to an array of M layers × N channels is straightforward. Ray-tracing simulations indicate that the bending loss is as small as 0.21 dB at the small curvature radius of 0.25 mm. Prototypes were fabricated by the photomask transfer method from two types of UV-curable resin; these prototypes exhibited 90° bending loss of 1.65 dB at a core curvature radius of 0.25 mm.     

Properties of steady-state in Er~(3 )-Yb~(3 )co-doped phosphate glass for optical waveguide laser

Transitions of laser diode(LD)pumped Er~(3 )-yb~(3 )co-doped glass laser are rather complicated.Consider- ing energy transfer between Er~(3 )and Yb(3 )ions,cross-relaxation,upconversion luminescence,and other transition processes,rate equations of quasi-three energy-level-system of the Er~(3 )-yb~(3 )co-doped laser are presented.The output characteristics are also calculated and analyzed in detail.The results show that Er~(3 )-yb~(3 )co-doped phosphate waveguide lasers with high slope efficiency and low threshold can be achieved.     

The optimal design for weak optical feedback semiconductor laser with frequency modulation

In this paper the frequency modulation characteristics the semiconductor laserwith weak optical feedback are presented,considering both the frequency deviation and thespurious intensity modulation.The frequency modulation can be realized without spurious in-tensity modulation under proper feedback conditions.There is an optimal feedback intensity tomaximize the frequency deviation.     

A quasi-vector finite difference mode solver for optical waveguides with step-index profiles

A finite difference scheme based on the polynomial interpolation is constructed to solve the quasi-vector equations for optical waveguides with step-index profiles. The discontinuities of the normal components of the electric field across abrupt dielectric interfaces are taken into account. The numerical results include the polarization effects, but the memory requirement is the same as in solving the scalar wave equation. Moreover, the proposed finite difference scheme can be applied to both uniform and non-uniform mesh grids. The modal propagation constants and field distributions for a buried rectangular waveguide and a rib waveguide are presented. Solutions are compared favorably with those obtained by the numerical approaches published earlier.     

Two-dimensional novel optical lattices with multi-well traps for cold atoms or molecules

We propose some new schemes to constitute two-dimensional (2D) array of multi-well optical dipole traps for cold atoms (or molecules) by using an optical system consisting of a binaryπ-phase grating and a 2D array of rectangle microlens. We calculate the intensity distribution of each optical well in 2D array of multi-well traps and its geometric parameters and so on. The proposed 2D array of multi-well traps can be used to form novel 2D optical lattices with cold atoms (or molecules), and form various novel optical crystals with cold atoms (or molecules), or to perform quantum computing and quantum information processing on an atom chip, even to realize an array of all-optical multi-well atomic (or molecular) Bose-Einstein condensates (BECs) on an all-optical integrated atom (or molecule) chip.     

New chemically stable Er_(3+)-Yb_(3+) co-doped phosphate glass for optical waveguide lasers and amplifiers

A set of phosphate glasses with different amounts of Al2O3, Na2O, La2O3 and AlF3 contents were prepared to search for a phosphate glass which is suitable for ion-exchange process. Based on chemical durability test results and spectroscopic properties, a glass with excellent chemical durability and good spectroscopic properties is developed for ion-exchange process. The emission cross section of Er3+ in this glass is calculated to be 0.72×10~20 cm2 by McCumber theory. The planar waveguide with three modes at 632.8 nm and one mode at 1540 nm can be realized by 335℃ 3 hours ion-exchange in 5%AgNO3+95%KNO3 molten salt.