10 GHz optical short pulse generation using tandem electroabsorption modulators monolithically integrated with distributed feedback laser by ultra-low-pressure selective area growth

In this work, a novel light source of tandem InGaAsP/InGaAsP multiple quantum well electroabsoption modulator( EAM ) monolithically integrated with distributed feedback laser is fabricated by ultra-low-pressure ( 22 x 10(2) Pa ) selective area growth metal-organic chemical vapor diposition technique. Superior device performances have been obtained, such as low threshold current of 19 mA, output light power of 4.5 mW, and over 20 dB extinction ratio at 5 V applied voltage when coupled into a single mode fiber. Over 10 GHz 3dB bandwidth in EAM part is developed with a driving voltage of 2 V. Using this sinusoidal voltage driven integrated device, 10 GHz repetition rate pulse with an actual width of 13.7 ps without any compression elements is obtained due to the gate operation effect of tandem EAMs.

Tandem electroabsorption modulators integrated with DFB laser by ultra-low-pressure selective-area-growth MOCVD for 10 GHz optical short pulse generation - art. no. 60200O

A novel device of tandem multiple quantum wells (MQWs) electroabsorption modulators (EAMs) monolithically integrated with DFB laser is fabricated by ultra-low-pressure (22 mbar) selective area guowth (SAG) MOCVD technique. Experimental results exhibit superior device characteristics with low threshold of 19 mX output light power of 4.5 mW and over 20 dB extinction ratio when coupled into a single mode Fiber. Moreover, over 10 GHz modulation bandwidth is developed with a driving voltage of 2 V. Using I this sinusoidal voltage driven integrated device, 10GHz repetition rate pulse with a width of 13.7 ps without any compression elements is obtained.

Highly efficient photoluminescence of Er2SiO5 films grown by reactive magnetron sputtering method

E2SiO5 thin films were fabricated on Si substrate by reactive magnetron sputtering method with subsequent annealing treatment. The morphology properties of as-deposited films have been studied by scanning electron microscope. The fraction of erbium is estimated to be 23.5 at% based on Rutherford backscattering measurement in as-deposited Er-Si-O film. X-ray diffraction measurement revealed that Er2SiO5 crystalline structure was formed as sample treated at 1100 degrees C for 1 h in O-2 atmosphere. Through proper thermal treatment, the 1.53 mu m Er3+-related emission intensity can be enhanced by a factor of 50 with respect to the sample annealed at 800 degrees C. Analysis of pump-power dependence of Er3+ PL intensity indicated that the upconversion phenomenon could be neglected even under a high photon flux of 10(21) (photons/cm(2)/sec). Temperature-dependent photoluminescence (PL) of Er2SiO5 was studied and showed a weak thermal quenching factor of 2. Highly efficienct photoluminescence of Er2SiO5 films has been demonstrated with Er3+ concentration of 10(22)/cm(3), and it opens a promising way towards future Si-based light source for Si photonics. (C) 2009 Elsevier B.V. All rights reserved.

Design of a compact polarizing beam splitter based on a photonic crystal ring resonator with a triangular lattice

We propose and simulate a new kind of compact polarizing beam splitter (PBS) based on a photonic crystal ring resonator (PCRR) with complete photonic bandgaps. The two polarized states are separated far enough by resonant and nonresonant coupling between the waveguide modes and the microring modes. Some defect holes are utilized to control the beam propagation. The simulated results obtained by the finite-difference time-domain method show that high transmission (over 95%) is obtained and the polarization separation is realized with a length as short as 3.1 mu m. The design of the proposed PBS can be flexible, thanks to the advantages of PCRRs.

Ultracompact triplexer by coupling and decoupling of multiple photonic crystal waveguides

We investigate numerically the self-imaging effect in a system of multiple coupled photonic crystal waveguides (M-CPCWs) with asymmetric coupling. Then two couplers of 2-CPCWs and 3-CPCWs are cascaded to form an ultracompact triplexer by employing coupling and decoupling of M-CPCWs. The wavelength of 1310 nm propagates along the input direction because the M-CPCWs are decoupled at the same decoupling frequency. The other two wavelengths (1490 and 1550 nm) are separated by combining multimode interference and the dual mode coupling effect. Only by introducing a single defect near the crossing point between two output photonic crystal waveguides (PCWs) are the high extinction ratios for the three wavelengths achieved simultaneously.

Effects of GaN Capping on the Structural and the Optical Properties of InN Nanostructures Grown by Using MOCVD

InN nanostructures with and without GaN capping layers were grown by using metal-organic chemical vapor deposition. Morphological, structural, and optical properties were systematically studied by using atomic force microscopy, X-ray diffraction (XRD) and temperature-dependent photoluminescence (PL). XRD results show that an InGaN structure is formed for the sample with a GaN capping layer, which will reduce the quality and the IR PL emission of the InN. The lower emission peak at similar to 0.7 eV was theoretically fitted and assigned as the band edge emission of InN. Temperature-dependent PL shows a good quantum efficiency for the sample without a GaN capping layers; this corresponds to a lower density of dislocations and a small activation energy.

Proposal of an Ultracompact Triplexer Using Photonic Crystal Waveguide with an Air Holes Array

We propose an ultracompact triplexer based on a shift of the cutoff frequency of the fundamental mode in a planar photonic crystal waveguide (PCW) with a triangular lattice of air holes. The shift is realized by modifying the radii of the border holes adjacent to the PCW core. Some defect holes are introduced to control the beam propagation. The numerical results obtained by the finite-difference time-domain method show that the presented triplexer can separate three specific wavelengths, i.e. 1310, 1490 and 1550 nm with the extinction ratios higher than - 18 dB. The designed device with a size as compact as 12 mu m x 6.5 mu m is feasible for the practical application, and can be utilized in the system of fiber to the home.

Role of Bi3+ ions for Er3+ ions efficient 1.54 mu m light emission in Er/Bi codoped SiO2 thin film prepared by sol-gel method

Er/Bi codoped SiO2 thin films were prepared by sol-gel method and spin-on technology with subsequent annealing process. The bismuth silicate crystal phase appeared at low annealing temperature while vanished as annealing temperature exceeded 1000 degrees C, characterized by X-ray diffraction, and Rutherford backscattering measurements well explained the structure change of the films, which was due to the decrease of bismuth concentration. Fine structures of the Er3+-related 1.54 mu m light emission (line width less than 7 nm) at room temperature was observed by photoluminescence (PL) measurement. The PL intensity at 1.54 gm reached maximum at 800 degrees C and decreased dramatically at 1000 degrees C. The PL dependent annealing temperature was studied and suggested a clear link with bismuth silicate phase. Excitation spectrum measurements further reveal the role of Bi3+ ions for Er3+ ions near infrared light emission. Through sol-gel method and thermal treatment, Bi3+ ions can provide a perfect environment for Er3+ ion light emission by forming Er-Bi-Si-O complex. Furthermore, energy transfer from Bi3+ ions to Er3+ ions is evidenced and found to be a more efficient way for Er3+ ions near infrared emission. This makes the Bi3+ ions doped material a promising application for future erbium-doped waveguide amplifier and infrared LED

Anisotropy of magnetic properties in ferrimagnetic ytterbium iron garnet under high magnetic fields

The magnetic anisotropy in ytterbium iron garnet (YbIG) is theoretically investigated under high magnetic fields (up to 160 kOe). According to the crystal field effect in ytterbium gallium garnet (YbGaG), a detailed discussion of crystal-field interaction in YbIG is presented where a suitable set of crystal-field parameters is obtained. Meanwhile, the influences of nine crystal-field parameters on the crystal-field energy splitting are analyzed. On the other hand, considering the ytterbium-iron (Yb-Fe) superexchange interaction of YbIG, the spontaneous magnetization is calculated at different temperatures for the [111] direction. In particular, we demonstrate that the Wesis constant lambda is the function of 1/T in YbIG. In addition, the field dependences of the magnetization for the [110] and [111] directions are theoretically described where a noticeable anisotropy can be found. Our theory further confirms the great contribution of anisotropic Yb-Fe superexchange interaction to the anisotropy of the magnetization in YbIG. Moreover, our theoretical results are compared with the available experiments.

Properties of exchange interaction in Yb3Fe5O12 under extreme conditions

In Yb3Fe5O12, the exchange effective field can be expressed as H-eff = -lambda center dot center dot center dot M-Fe = -lambda chi(eff)center dot center dot center dot H-e = -gamma center dot center dot center dot H-e where gamma is named as the exchange field parameter and H-e is the external magnetic field. Then, in this paper, by the discussions on the characteristics of the exchange field parameter gamma, the properties of exchange interaction in ytterbium iron garnet (Yb3Fe5O12) are analyzed under extreme conditions (high magnetic fields and low temperatures). Our theory suggests that the exchange field parameter gamma is the function of the temperatures under different external magnetic fields, and gamma = a+b center dot center dot center dot T+c center dot center dot center dot T-2, where the coefficients a, b, c are associated with the external magnetic fields and the magnetized directions. Thus, the temperature-dependence, field-dependence and anisotropic characteristics of the exchange interaction in Yb3Fe5O12 are revealed. Also, excellent fits to the available experiments are obtained. (C) 2009 Elsevier B.V. All rights reserved.

A new way of uniform splitting of the optical power by directional coupling between the photonic crystal waveguides

Directional coupler can be constructed by putting multiple photonic crystal waveguides together. The propagation of the optical field entering this system symmetrically was analysed numerically according to self-imaging principle. On the basis of this structure, ultracompact multiway beam splitter was designed and the ones with three and four output channels were discussed in details as examples. By simply tuning the effective refractive index of two dielectric rods in the coupler symmetrically to induce the redistribution of the power of the optical field, uniform or free splitting can be achieved. Compared with the reported results, this way is simpler, more feasible and more efficient and has extensive practical value in future photonic integrated circuits.

1 x 4 Ge-on-SOI PIN Photodetector Array for Parallel Optical Interconnects

High-quality Ge film was epitaxially grown on silicon on insulator using the ultrahigh vacuum chemical vapor deposition. In this paper, we demonstrated that the efficient 1 4 germanium-on-silicon p-i-n photodetector arrays with 1.0 mu m Ge film had a responsivity as high as 0.65 A/W at 1.31 mu m and 0.32 A/W at 1.55 mu m, respectively. The dark current density was about 0.75 mA/cm(2) at 0 V and 13.9 mA/cm(2) at 1.0 V reverse bias. The detectors with a diameter of 25 mu m were measured at 1550 nm incident light under 0 V bias, and the result showed that the 3-dB bandwidth is 2.48 GHz. At a reverse bias of 3 V, the bandwidth is about 13.3 GHz. The four devices showed a good consistency.

Electroabsoorption-modulated laser light-source module using selective area growth for 10 Gb/s transmission

In this work, a novel light source of strained InGaAsP/InGaAsP MQW EAM monolithically integrated with DFB laser is fabricated by ultra-low-pressure (22 x 10(2) Pa) selective area growth ( SAG) MOCVD technique. Superior device performances have been obtained, sue h as low threshold current of 19 mA, output light power of about 7 mW, and over 16 dB extinction ratio at 5 V applied voltage when coupled into a single mode fiber. Over 10 GHz 3 dB bandwidth in EAM part is developed with a driving voltage of 3 V. After the chip is packaged into a 7-pin butterfly compact module, 10-Gb/s NRZ transmission experiments are successfully performed in standard fiber. A clearly-open eye diagram is achieved in the module output with over 8.3 dB dynamic extinction ratio. Power penalty less than 1.5 dB has been obtained after transmission through 53.3 km of standard fiber, which demonstrates that high-speed, low chirp EAM/DFB integrated light source can be obtained by ultra-low-pressure (22 x 102 Pa) SAG method.

Thermally Stable Guest-Host Polyetherketone Poled Polymer for Electro-Optical Applications

The high glass transition temperature polymer polyetherketone doped with disperse red 13 (DR13/PEK-c) has been prepared by the spin-coating method. Through in situ second-harmonic generation, the corona poling temperature was optimized by measuring the temperature dependence of the in situ second-harmonic generation signal intensity under the poling electric field. The linear electro-optic coefficients of the poled polymer films have been determined at 632.8 nm by using a simple interferometric technique. The polymer system was measured after 13 000 h, and found that it remained at 80% of its initial value.

On the nature of iron in InP: A FTIR study

Fe is still the commonly used dopant to fabricate semi-insulating(SI) InP, a key material for high-speed electronic and optoelectronic devices. High resolved absorption spectra of the internal d-d shell transitions at Fe2+ in InP and the related phonon sidebands and a series of iron related absorption Lines are presented. Detailed infrared absorption study of the characteristic spectra of four zero-phonon lines(ZPLs), which are attributed to transitions within the 5D ground state of Fe2+ (3d(6)) on the indium site in a tetrahedral crystal field of phosphorus atoms and their temperature effects are given.