There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Electronic circuits provide us with the ability to control the transport and storage of electrons. However, the performance of electronic circuits is now becoming rather limited when digital information needs to be sent from one point to another. Photonics offers an effective solution to this problem by implementing optical communication systems based on optical fibers and photonic circuits. Unfortunately, the micrometer-scale bulky components of photonics have limited the integration of these components into electronic chips, which are now measured in nanometers. Surface plasmon-based circuits, which merge electronics and photonics at the nanoscale, may offer a solution to this size-compatibility problem. Here we review the current status and future prospects of plasmonics in various applications including plasmonic chips, light generation, and nanolithography.

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Plasmonics: merging photonics and electronics at nanoscale dimensions.

We present models for the optical functions of 11 metals used as mirrors and contacts in optoelectronic and optical devices: noble metals (Ag, Au, Cu), aluminum, beryllium, and transition metals (Cr, Ni, Pd, Pt, Ti, W). We used two simple phenomenological models, the Lorentz-Drude (LD) and the Brendel-Bormann (BB), to interpret both the free-electron and the interband parts of the dielectric response of metals in a wide spectral range from 0.1 to 6 eV. Our results show that the BB model was needed to describe appropriately the interband absorption in noble metals, while for Al, Be, and the transition metals both models exhibit good agreement with the experimental data. A comparison with measurements on surface normal structures confirmed that the reflectance and the phase change on reflection from semiconductor-metal interfaces (including the case of metallic multilayers) can be accurately described by use of the proposed models for the optical functions of metallic films and the matrix method for multilayer calculations.

Optical properties of metallic films for vertical-cavity optoelectronic devices.

Recent advances in the exploitation of localized surface plasmons (charge density oscillations confined to metallic nanoparticles and nanostructures) in nanoscale optics and photonics, as well as in the construction of sensors and biosensors, are reviewed here. In particular, subsequent to brief surveys of the most-commonly used methods of preparation and arraying of materials with localized surface plasmon resonance (LSPR), and of the optical manifestations of LSPR, attention will be focused on the exploitation of metallic nanostructures as waveguides; as optical transmission, information storage, and nanophotonic devices; as switches; as resonant light scatterers (employed in the different near-field scanning optical microscopies); and finally as sensors and biosensors.

Exploitation of Localized Surface Plasmon Resonance

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Principles Of Optics Electromagnetic Theory Of Propagation Interference And Diffraction Of Light

A description is given of the research progress in developing a vertical-cavity surface-emitting (SE) injection laser based on GaAlAs/GaAs and GaInAsP/InP systems Ultimate laser characteristics, device design, state-of-the-art performances, possible device improvement, and future prospects will also be discussed The authors propose a vertical-cavity surface emitting semiconductor laser To reduce the threshold current, they improved the laser reflector and introduced a circular buried heterostructure The microcavity structure, which is 7 mu m long and 6 mu m in diameter, was realized with a threshold of 6 mA Thus, possibilities of an extremely low threshold current SE laser device and a densely packed two-dimensional array are suggested >

Surface emitting semiconductor lasers

A general formula is given that expresses frequency chirping in some types of external intensity modulators, such as the loss modulator, directional-coupler-type modulator, Mach-Zehnder interferometry-type modulator, and total-internal-reflection-type modulator. The chirping phenomenon treated is caused by the phase modulation due to an accompanied refractive index change. It is uniquely expressed in terms of an alpha -parameter that contributes to frequency chirping in the same manner as in the direct modulation of a semiconductor laser. In addition, the transmission bandwidth of a single-mode fiber system using an external modulator is discussed and compared with the results obtained utilizing direct laser modulation. >

Frequency chirping in external modulators

A vertical-cavity surface emitting laser (VCSEL) was invented 30 years ago. A lot of unique features can be expected, such as low-power consumption, wafer-level testing, small packaging capability, and so on. The market of VCSELs has been growing up rapidly in recent years, and they are now key devices in local area networks using multimode optical fibers. Also, long wavelength VCSELs are currently attracting much interest for use in single-mode fiber metropolitan area and wide area network applications. In addition, a VCSEL-based disruptive technology enables various consumer applications such as a laser mouse and laser printers. In this paper, the recent advance of VCSEL photonics will be reviewed, which include the wavelength extension of single-mode VCSELs and their wavelength integration/control. Also, this paper explores the potential and challenges for new functions of VCSELs toward optical signal processing

https://cnst.nctu.edu.tw/mbe08/abstract/6-13.30-14.00-koyama.pdf

Recent Advances of VCSEL Photonics

Room‐temperature continuous wave (cw) operation of a GaAs vertical microcavity surface‐emitting laser has been achieved. An ultrashort cavity device with a cavity length of ∼5.5 μm was grown by metalorganic chemical vapor deposition. cw lasing characteristics such as mode properties and temperature characteristics were examined. Single longitudinal mode operation with a side mode suppression ratio of 35 dB was obtained. The temperature range for single mode operation was more than 50 K.

Room-temperature continuous wave lasing characteristics of a GaAs vertical cavity surface-emitting laser

The spontaneous emission factor (SEF) of a microcavity distributed Bragg reflector (DBR) surface-emitting laser has been obtained theoretically to investigate the possibility of the thresholdless lasing operation. Formulas expressing the spontaneous emission in a three-dimensional microcavity were obtained. By introducing the distribution of mode density in wavevector space, it is shown that the radiation pattern of spontaneous emission is deeply modified by the microcavity and is different from that in free space. Based on this result, the SEF and the emission lifetime are calculated as a function of emission spectral width and the size of the active region. It is found that the SEF exceeds 0.1, even though the spectral width is as large as 30 nm when the transverse size is smaller than 0.5 mu m and the DBR reflectivity is larger than 90%. >

Fumio Koyama

Papers

Surface emitting semiconductor lasers

Frequency chirping in external modulators

Recent Advances of VCSEL Photonics

Room-temperature continuous wave lasing characteristics of a GaAs vertical cavity surface-emitting laser

Spontaneous emission factor of a microcavity DBR surface-emitting laser