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The thermomechanical reliability of surface mount components (SMCs) is closely related to the reflow soldering process. With the rise of board complexity, an optimal reflow profile must consider the mix of large and small components, the density of the components on the board, and the board dimensions. It has been a significant challenge to achieve uniform temperature on SMCs with different sizes and different thermal masses, such as capacitors, transistors, quad-flat no-leads (QFN), and ball grid array (BGA) packages. To reflow large components such as BGA packages, the minimum reflow temperature should be reached, meanwhile, the temperature should not exceed the damaging temperature of the smaller or heat-sensitive components. The recommended reflow profile is defined as a band or process window. To achieve good quality soldering, the temperature applied to the solder under varied sizes of components should be within the recommended band. This article introduces a numerical method based on a compact model to predict the reflow profile for bulky BGA packages. The impinging gas temperature is used as the boundary condition to predict the temperature distribution throughout a board with different sized components. The proper oven temperature setting to achieve the ideal profiles is obtained finally. [ABSTRACT FROM AUTHOR]

In the field of physical oceanography, the temperature and pressure of seawater are important fundamental parameters. In order to realize the simultaneous measurement of the temperature and pressure in seawater, a reflective optical fiber sensor based on polydimethylsiloxane (PDMS)-sealed optical microfiber coupler combined with a sagnac loop (OMCSL) is proposed. Benefiting from the high thermo-optical coefficient and large elasticity of PDMS, and the large-scale swift field transmission characteristics of optical microfiber coupler (OMC), the sensitivity and structural stability of our sensor is largely improved. The response performance of the sensor is further analyzed by numerical simulation calculations and theoretical modeling. Experimental results show that the temperature and pressure sensitivity of the sensor could reach −2.133 nm/°C and 3.416 nm/Mpa, respectively, about one order higher than that of bare fiber OMCSL. Furthermore, via inversely calculating the cross-sensitivity matrix, the temperature and pressure sensing can be demodulated simultaneously, and the average errors of the preliminary experimental settlements are 1.61% and 5.02%, respectively. Due to the merits of compact structure, easy fabrication, high sensitivity, fast response speed and high stability, the basic performance of this dual parametric sensor is comparable to the existing electrical temperature-depth (TD) sensor, which is expected to meet the practical application requirements of marine environmental monitoring and ocean dynamics research. [ABSTRACT FROM AUTHOR]

Compared with traditional dyes, structural color has been studied widely due to several outstanding advantages. When choosing structural color materials, both metal and dielectric materials have great potential, however compared with metal, dielectric material have the characteristics of low cost and low loss, so been studied widely. At present, the design of metasurface structural color based on dielectric materials is mostly carried out by manually adjusting parameters. Although good results can achieved by this method, but the design cycle is too long and the method is not smart enough, which is not conducive to industrial design. In this article, we proposed a combination of intelligent algorithms and finite domain time domain solution, and designed matesurface structural color successfully that can reflect high-quality colors. The reflection peak value of the RGB colors reached 90%, 82.2%, 45.8% respectively, also accompany with narrow FWHM, the designed structural color has strong robustness and method reusability, meanwhile, our work provides a novel way for the design of reflective structural color. [ABSTRACT FROM AUTHOR]

We propose and demonstrate an all-optical tunable polymer bottle micro-resonator fabricated by droplet dispensing method. A microfiber is used to excite whispering gallery mode (WGM) of the micro-resonator. Continuous wave (CW) laser is employed as pump light to tune the WGM. To illustrate tuning performance of the fabricated device, external and internal pump light methods are both employed. For external pump light method, the tuning efficiency is about 5.23 pm/mW. For internal pump light, tuning efficiency of 68.3 pm/mW is obtained. The experimental results reveal that the bottle micro-resonator (BMR) can achieve wavelength tuning more than one free spectral range (FSR), which indicates the WGM can be tuned within a transparent window covered the full wavelength range. In addition, the fabricated device has advantages of high tuning efficiency, small size, easy fabrication, and extremely low cost. [ABSTRACT FROM AUTHOR]

Reconfigurable optical add-drop multiplexer (ROADM) is one of the key building blocks for on-chip optical networks, which can download the desired signals from the bus waveguide to the corresponding drop port and upload the local signals from the add port to the bus waveguide to achieve the signals dropping/adding between the local and the bus waveguide. In this letter, we propose a ROADM based on a Benes network for mode-division multiplexing systems. As a proof of the concept, a ROADM with three quasi-transverse electric modes (TE0-TE2) is fabricated and experimentally demonstrated, which can download signals from TEi (i = 0, 1, 2) mode channel in the bus waveguide to an arbitrary local drop port or upload local signals to TEi mode channel via an arbitrary add port. The excess loss of the fabricated device is less than 10.7 dB, and the crosstalk among different space or mode channels is lower than −13.7 dB. Finally, a 12 Gbps data transmission experiment is carried out to verify the performance of the device. The proposed device is reconfigurable and scalable, and thus, it is expected to be used for optical data processing in the mode-division multiplexing systems. [ABSTRACT FROM AUTHOR]

A mid-infrared (mid-IR) dual-band filter with ultra-high resolving power is designed and numerically investigated. It is composed of an Al2O3 layer between a gold grating and a CaF2 substrate. Each unit cell of the grating consists of two gold strips with different heights. The filter provides two high-extinction ultra-narrow stop bands. One is at a wavelength of ∼3.8392 μm with a full-width at half-maximum (FWHM) of ∼0.8 nm, and the other is at a wavelength of ∼3.8435 μm with a FWHM of ∼1.8 nm. The resolving power of the filter is >2100. The two stop bands result from the (+1) and (−1) waveguide modes, respectively. An interaction between the two resonance modes exists and affects the stop bands. We can control the interaction by adjusting the grating parameters, thus designing the FWHMs and lineshapes of the two stop bands flexibly. [ABSTRACT FROM AUTHOR]

An all optical fiber CTD sensor used in seawater based on an OMC is demonstrated. And the OMC is fabricated by fusing and tapering two twisted conventional communication fibers based on the improved flame-brushing method. By monitoring the sensing dips, in situ measurement of salinity, temperature, and depth (pressure) in seawater can be realized, respectively. Especially, the water depth (pressure) sensing function of the OMC is demonstrated for the first time, and the pressure sensitivity is 50 times higher than a bare fiber Bragg grating (with a wide pressure measurement range from 0 to 25 MPa). The highest sensitivities of salinity, temperature, and depth are 1596 pm/‰, 2326 pm/°C, and 169 pm/Mpa, respectively. These are high enough for the requirements of marine dynamic environmental monitoring and underwater target detection of fiber-optic hydrophone system. The all optical fiber CTD sensor demonstrated here show advantages of easy fabrication, compact structure, high sensitivity, low cost, and compatibility with the optical fiber system, which may find applications in multifunction optical sensors in ocean detections and other applications. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the characteristics of all-optical modulation via thermo-optic effects of an optical microfiber coupler (OMC) and the theoretical analysis and experimental results are shown. The intensity modulation and the phase modulation efficiency are proportional to the length of the OMC' waist region, the pump light intensity, etc. We experimentally characterize the OMC, presenting that stable intensity and phase modulation can be realized by pumps at microwatts level. For OMC' intensity modulation, the modulation bandwidth is measured to be 50 kHz under 1.7 mW pump light intensity. We also demonstrate OMC's phase modulation function, and the frequency response characteristics of the OMC phase modulator shows similar properties with the OMC's intensity modulation, which mainly depends on the waveguide structures of the OMC' waist region and the heat conduction property of the waveguide materials. These results are valuable for the development of all-optical modulators and all-optical tunable filters based on subwavelength scales optical fiber, and hold great potential in laser and optical sensing applications. [ABSTRACT FROM AUTHOR]

A new beam deflector and optical coupler structure based on plasmonic nano-slits is proposed and numerically investigated. The structure consists of periodic nano-slits array with the same width and interval. All nano-slits are etched on a silver film whose dimension D is 7~\mu \textm (The transverse span of the structure). Arbitrary deflection angle can be selected for reflected light by adjusting the size of the nano-slits, the effective refractive index, and the interval of the nano-slits. This structure also can act as an optical coupler by placing a medium on the top of the nano-slits array with specific size and refractive index. The coupling efficiency can approach to 80.73%, and it provides a promising way to design and manufacture future compact optical communication device. [ABSTRACT FROM PUBLISHER]

A multilayer graphene-based tunable bandpass filter is proposed by using cascaded silicon microring resonators. Six graphene layers are embedded in the silicon-on-insulator waveguide to enhance the influence on the effective mode index, and a pretreatment has also been implemented to compensate the coupling-induced resonance frequency shifts. By tuning the Fermi level of the graphene, the position of the pass band can be dynamically modulated in the whole communication $C$ -band. The out-of-band extinction ratio of drop port can be larger than 40 dB; the 3-dB bandwidths of the pass bands are over 2.8 nm, and the insertion loss is less than 1.5 dB. [ABSTRACT FROM PUBLISHER]

The transmission characteristics of asymmetrical multi-teeth-shaped plasmonic waveguide structure are investigated theoretically and numerically. The tunable dual flat bandgaps are achieved in our proposed structure. This feature can provide a promising application for plasmonic bandstop filter. In addition, according to the hybrid effects of the first order resonance and high order resonance of $N$ identical asymmetrical teeth, a sharp transmission peak can be obtained. This peak, which is within two bandgaps, possesses a relative small full-width at half-maximum, about 11.5 nm. Moreover, the resonant wavelength of this sharp peak can be regulated by adjusting the relative depths of $N$ asymmetrical teeth. These results that we acquire may have important application potential on high-density nanoplasmonic integration circuits. [ABSTRACT FROM PUBLISHER]

We propose a novel broadband beam splitter (BS) with a single-layer and compact grating vertical coupling structure, which is based on the form birefringence of subwavelength binary blazed grating and effective-medium theory. Rigorous coupled-wave analysis is used to optimize the design of this beam splitter. The simulation and analysis show that the BS for transverse electric (TE) light are designed to split the incident light beam into two beams of equal power (nearly 50% split), which travel in opposite directions in the waveguide. The coupling length is about 9 \mu\m. The coupling efficiency for the right and the left branches of waveguide are 47% and 52%, respectively. The power difference of two output ports is less than 15% over a 75-nm wavelength bandwidth range. [ABSTRACT FROM PUBLISHER]