Thin Film Filter for Broadband IR Integrated Waveguide Amplifiers

A new S-type of IR integrated waveguide amplifiers, based on erbium-ytterbium co-doped phosphate glass integrated with medium thin film filter, is proposed. The intrinsical gain spectrum of the proposed amplifier is obtained by solving rate and power propagation equations, a thin film filter flattening this intrinsical gain spectrum is designed by genetic algorithm, and fabricated. An average gain >10dB is obtained between 1530nm and 1560nm, and the average gain about 18dB between 1531nm and 1550nm with gain difference of <3dB is achieved.     

基于长周期光栅的宽带磷酸盐玻璃波导放大器

提出一种基于长周期波导光栅的宽带集成Er-Yb掺杂磷酸盐玻璃集成波导放大器,其中增益平坦光栅滤波器直接刻蚀在有源波导上.放大器模型建立在考虑了上转换之后的传输与速率方程基础上,利用重叠积分与龙格-库塔相结合的方法进行求解.放大器的本征增益谱通过求解重叠积分龙格-库塔方程得到,放大器的有害增益峰由长周期波导光栅滤波器来消除.讨论了长周期波导光栅透射谱对放大器增益平坦的影响.数值计算结果表明,在1 532～1 565 nm范围内,放大器的平均增益约为20 dB,增益抖动小于3 dB.研究结果表明,该结构可有效地消除本征增益谱中的峰值增益,提高放大器的增益平坦带宽.     

Silicon Photonic Wire Filter Using Asymmetric Sidewall Long-Period Waveguide Grating in a Two-Mode Waveguide

We demonstrate a silicon photonic wire filter using asymmetric sidewall long-period waveguide gratings for the first time. The proposed device consists of single-mode waveguide sections, a two-mode section with corrugated gratings, and taper sections to connect them. The operation of this device is based on the codirectional coupling between two core modes. By adopting a high refractive index contrast waveguide, the period and depth of grating are given as 4.44 m and 5 nm, respectively. Thus, the total length of long-period grating is significantly reduced to 260 m. The measured maximum attenuation at the center wavelength is about 13 dB. The bandwidth of the transmission dip is 15 nm. Finally, issues on the design and the performance of our device are discussed.     

S-type Er-Yb Co-doped Phosphate Glass Waveguide Amplifier Integrated with Cascaded Multilayer Medium Thin Film Filter

A new S-type of erbium-ytterbium co-doped phosphate glass waveguide amplifier integrated with cascaded multilayer medium thin film filter is proposed, this S-type geometry waveguide structure is used to achieve a long path in a compact chip,and obtained higher gain with lower Er-doped concentration. The cascaded multilayer medium thin film filter is utilized to achieve a broader flattening gain bandwidth. The intrinsical gain spectrum is obtained by solving rate and power propagation equations, the effect of transmittance spectrum of thin film filter on flattening gain is discussed.     

Realization of Long-Period Corrugated Grating in Silica-on-Silicon-Based Channel Waveguide

Long-period corrugated grating in silica-on-silicon-based channel waveguide is realized by making periodic corrugation on top of a relatively high-indexed (contrast ap.8%) Ge-doped silica waveguide, which is sandwiched between undoped silica undercladding and boro-phospho-silicate-glass overcladding layers. Resonance wavelength of the 15-mm-long grating is found at ~1581 nm, having negligible polarization dependency at room temperature, with a grating strength of ~11 dB and 3-dB bandwidth of 7 nm. The temperature characteristic of the grating is also investigated, which is found to be similar to that of the long-period fiber grating. This device has significant potential for various integrated-optic communication and sensing applications.     

Er–Yb Waveguide Amplifiers in Novel Silicate Glasses

A set of novel silicate glasses containing ZnO and co-doped with Er³⁺ and Yb³⁺ was designed as substrates for optical waveguide amplifiers. Characterized by exceptionally low up-conversion, minimum Er concentration quenching and high mechanical as well as chemical stability, the reported glasses can compete with phosphate-based materials typically used in the state-of-art active devices. Straight channel waveguides with propagation losses as low as 0.18 dB/cm were fabricated in these substrates using Ag⁺ hArr Na⁺ and K ⁺ hArr Na⁺ thermal ion exchange. Net on-chip gain values of 6.7 dB at 1537 nm were measured and a net fiber to-fiber gain of 5 dB was achieved when pumped at 976 nm. A six-level spatially resolved numerical model of an Er-Yb co-doped active waveguide was developed to analyze and optimize the amplifier performance. Modification of the rare-earth dopant concentration and the channel waveguide geometry was proposed to increase the gain figure and improve the overall amplifier efficiency.     

Design and Simulation of a Narrow Passband Electro-Optical Tunable Filter with Band-pass and Band-rejection Output

An electro-optical tunable filter comprised of two paralleled identical long-period waveguide gratings is proposed in this paper. The filter has one input port and two separate output ports, outputting band-pass and band-rejection light respectively. Using poled electro-optical polymer material to fabricate its waveguide cores enable the filter’s tuning speed to approach nanosecond order. With the aid of long-period waveguide gratings, the tuning range of the filter is Λ times larger than the conventional electro-optical filters. We built up a model to design and simulate the proposed tunable optical filter. We investigate the relationship between the parameters of the long-period waveguide grating and the characteristics of the tunable filter, such as tuning range and FWHM. The simulation results show that the tunable optical filter can realize high-speed tuning in the wavelength range of 1530 nm to 1560 nm, and the FWHM width can reach 0.8 nm. Compared with the conventional optical filters, the results show that a high-speed widely tunable optical filter with narrow pass band can be achieved.     

The Rectangular Waveguide Board Wall Slot Array Antenna Integrated with One Dimensional Subwavelength Periodic Corrugated Grooves and Artificially Soft Surface Structure

In this letter, we propose a high gain rectangular waveguide board wall slot array antenna, which is integrated with one dimensional subwavelength periodic corrugated grooves and artificially soft surface structure. The corresponding far field radiation characteristics are investigated. The simulation results show that the gain of planar 2 × 8 slot array antenna with the introduction of corrugated grooves structure is increased to 26.1 dB, and half power beamwidth in the E plane is considerably reduced. Compared with the subwavelength periodic grooves slits array antenna proposed by Huang et al.[Appl. Phys. Lett. 91, 143512 (2007)], the side and back lobe level of this antenna are also significantly reduced by 6 dB and 10 dB, respectively. The physical mechanism for radiation-pattern improvement has been well explained by the modulation of surface wave, the reradiation of surface energy, and suppression of surplus surface wave at the grounded edge.     

Optimization and fabrication of stitched long-period gratings for gain flattening of ultrawide-band EDFAs

We present the optimization and fabrication of the stitched long-period fiber gratings (SLPGs) for gain flattening of an ultrawide-band erbium-doped fiber amplifier (EDFA). With an improved genetic algorithm, the gain spectrum of a practical EDFA with bandwidth of 80 nm is flattened within /spl plusmn/0.69 dB by an optimized SLPG. Furthermore, the SLPG is designed specially for a point-by-point grating writing technique. A superior control of the fabrication procedure of the designed SLPG has been demonstrated in the experiment.     

Theoretical and Experimental Investigation of a Ka-band Gyro-TWT with Lossy Interaction Structure

The stability analysis of a Ka-band gyrotron traveling-wave tube amplifier (gyro-TWT) operating in the circular TE₀₁ mode at the fundamental cyclotron harmonic is presented. The small signal linear theory is used to analyze the amplification of operation mode and oscillation of parasitic modes. The optimum dielectric parameters including loss layer thickness and permittivity are given. Propagation loss of operation mode is 3 dB/cm with the thickness of loss layer d = 0.7 mm and relative permittivity ξ″ = 11−6j, and propagation loss per unit length of parasitic modes TE₁₁, TE₂₁, TE₀₂ at each oscillation frequency (24.85 GHz, 27.85 GHz, 61.2 GHz) is 2.5 dB/cm, 6 dB/cm, 7.5 dB/cm, respectively, sufficient to suppress oscillations of operation and parasitic modes. Taking advantage of the optimized parameters of loaded dielectric, a high gain scheme has been demonstrated in a 34-GHz, TE₀₁-mode gyro-TWT, producing 160 kW saturated output power at 40 dB stable gain and 22.8% efficiency with a 3-dB bandwidth of 5%.     

Fabrication and characterization of annealed proton exchanged long period waveguide grating in x-cut LiNbO3

In this paper, a long-period waveguide grating was fabricated in x-cut lithium niobate substrate by patterned annealed proton exchange waveguide fabrication process. The waveguide mode characteristic was evaluated using a charge-coupled device (CCD) camera. It shows that the waveguide is single mode transmission at a wavelength of 1 550 nm. The transmission spectra of the long period waveguide gratings were measured by optical spectrum analyzer (OSA) and show an extinction ratio of ~17 dB and a 3 dB bandwidth of ~10 nm at the resonant wavelength. The resonant wavelength moves toward to the long wavelength direction as the waveguide width-difference increases in the same period, and also shifts toward to the long wavelength direction with the increase of the period in the case of the same waveguide width-difference. The method of fabricating a long period waveguide grating based on a patterned annealed proton exchange technique simplifies the fabrication process, and at the same time, reduces the fabrication cost.     

Flexible,Low-loss Waveguide Designs for Efficient Coupling to Quantum Cascade Lasers in the Far-infrared

We coupled linearly polarized and azimuthally polarized Terahertz quantum cascade lasers (QCLs) to the low-loss optical modes of hollow core waveguides having a sequence of different metallic or dielectric inner coatings. The latter waveguides have been specifically designed to force the propagation of a dominant optical mode once the thickness (d) of the inner dielectric coating is properly chosen. Our results demonstrate that both the TE01 and the TE11 modes can be easily converted to a hybrid one when d > 6 μm allowing the propagation of THz QCL beams with transmission losses as low as 1.5 dB/m, bending losses < 1.1 dB and reasonably high coupling efficiencies (87%).     

基于SOI的16通道200GHz阵列波导光栅

设计并制作了基于绝缘体上硅(SOI)材料的1×16阵列波导光栅(AWG).该AWG器件的中心波长为1 550 nm,信道间隔为200 GHz,采用了脊型波导结构.首先确定了波导的结构尺寸以保证单模传输,并利用束传播法(BPM)模拟了波导间隔、弯曲半径和锥形波导长度等参数对器件性能的影响,对器件结构进行了优化,同时也利用BPM方法模拟了器件的传输谱.模拟结果显示:器件的最小信道损耗为4.64 dB,串扰小于-30 dB.根据优化的器件结构,通过光刻等半导体工艺制作了AWG,经测试得到AWG器件的损耗为4.52～8.1 dB,串扰为17～20 dB,能够实现良好的波分复用/解复用功能.     

集成光波导放大器波导截面面积的优化

从信号光及泵浦光在波导内的模式分布出发,提出了一种新的重迭因子的分析方法,对1 480 nm波段泵浦的掺铒光波导放大器(EDWA)进行了研究.探讨了光波导截面面积对EDWA增益的影响,得出了波导获得最大增益的波导截面面积范围,最后指出重迭因子是影响波导增益的一个重要方面.     

Fabrication and characterization of 1 550 nm polarization-insensitive semiconductor optical amplifiers

Semiconductor Optical Amplifiers (SOAs) can beused asin-line amplifier ,preamplifier ,optical switch,andwavelength converter in future optical systems[1-3].Po-larization-independent gain,high output power and lowgain ripple are desirable features for most…     

A Ka-band Four-stage Self-biased Monolithic Low Noise Amplifier

A Ka-band four-stage self-biased monolithic low noise amplifier has been developed using a commercial 0.18-μm pseudomorphic high electron-mobility transistor (pHEMT) process. For the application of self-bias technique, the low noise amplifier (LNA) is biased from a single power supply rail. The LNA has achieved a broadband performance with a gain of more than 18 dB, a noise figure of less than 3.8 dB in the RF frequency of 26 to 40 GHz. The chip size is 3 × 1 mm².     

Compact high gain erbium-ytterbium doped waveguide amplifier fabricated by Ag-Na ion exchange

A report is presented on an erbium-ytterbium doped waveguide amplifier fabricated by Ag-Na ion-exchange in a commercial phosphate glass substrate. The 31 mm-long active waveguide provides a maximum internal gain of 5.3 dB/cm at 1534 nm. The amplifier was fully characterised in terms of gain spectrum, noise figure, pump efficiency and gain saturation.     

用于S波段光纤拉曼放大器增益平坦的长周期光纤光栅设计

根据实际所测得的S波段光纤拉曼放大器的信号增益谱,通过对长周期光纤光栅具体参数的选定,由两个长周期光纤光栅级联滤波的组合,可以使增益图谱在50 nm(1485-1535 nm)带宽内,增益平坦度达到±0.6dB以内.由三个长周期光纤光栅级联滤波组合,可以使增益图谱在49 nm(1490-1539 nm)带宽内,增益平坦度达到0.5 dB, 55 nm(1485-1540 nm)带宽内,增益平坦度达到1 dB.这对扩大长周期光纤光栅增益平坦滤波器的运用范围,扩大单泵浦S波段光纤拉曼放大器的有效增益带宽有着积极的意义.     

Flat-top silica-based arrayed waveguide grating with 40-channels

A wavelength multiplexer or demultiplexer plays ani mportant role in all wavelength division multiplexing( WDM) system.Silica-basedarrayed waveguide gratings(AWGs) offer attractive featuresinthis area due to theadvantage of large output channels and lowlo…     

Coplanar Waveguide Fed Printed Antenna with Compact Size for Broadband Wireless Applications

A novel and simple coplanar waveguide fed compact antenna is introduced in this paper. The antenna structure combines the advantages of CPW with those of the broadband antenna and simplifies the structure of the antenna by reducing the number of metallization level to construct uni-planar antenna. Prototype of the proposed antenna have been constructed and studied experimentally. The measured results agrees well with the simulated prediction and shows a broad bandwidth of 6 GHz ranging from 3.5 GHz to 9.5 GHz with VSWR ≤2 (return loss ≤−10 dB), which is equivalent to 92.3% impedance bandwidth centered at 6.5 GHz. The proposed antenna shows stable radiation characteristics, gain and axial ratio of less than 1 dB over the whole operating bandwidth. Furthermore, an extensive parametric study was performed to realize the relationship between the resonance frequencies of the broadband antennas and different parameters which is helpful for advancement of the antenna design.