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Quantum Electronics
Abstract
The thirteen years that have intervened since the appearance of the second edition of this book have witnessed some important developments in the field of lasers and quantum electronics. Foremost among them are: phase-conjugate optics and its myriad applications, the long wavelength quaternary semiconductor laser, and the deepened understanding of the physics of semiconductor lasers—especially that applying to their current modulation and limiting linewidth, laser arrays and the related concept of supermodes, quantum well semiconductor lasers, the role of phase amplitude coupling in laser noise, and free-electron lasers. The present edition retains nearly all the material of the second edition. There are four new chapters on semiconductor lasers, quantum well lasers, free-electron lasers, and phase-conjugate optics. In addition, the chapters on laser noise and third-order nonlinear effects have been extensively revised.
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Stevenson, R. M., Astratov, V. N., Skolnick, M. S., Whittaker, D. M., Emam-Ismail, M., Tartakovskii, A. I., Savvidis, P. G., Baumberg, J. J., & Roberts, J. S. (2000) · Physical Review Letters · doi:10.1103/physrevlett.85.3680 · Cited by 446
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van Tilborg, J., Schroeder, C. B., Filip, C. V., Tóth, C., Geddes, C. G. R., Fubiani, G., Huber, R., Kaindl, R. A., Esarey, E. H., & Leemans, W. P. (2006) · Physical Review Letters · doi:10.1103/physrevlett.96.014801 · Cited by 189
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Al'Miev, I. R., Larroche, O., Benredjem, D. E., et al. (2007) · Physical Review Letters · doi:10.1103/physrevlett.99.123902 · Cited by 48
Minami, Y., Nakajima, M., & Suemoto, T. (2011) · Physical Review A · doi:10.1103/physreva.83.023828 · Cited by 48
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Production of multicharged atomic ions from laser-induced multiple ionization of small molecules
Hering, P., & Cornaggia, C. (1998) · Physical Review A · doi:10.1103/physreva.57.4572 · Cited by 44
Formation of Optical Bullets in Laser-Driven Plasma Bubble Accelerators
Dong, P., Reed, S. A., Yi, S. A., Kalmykov, S., Shvets, G. B., Downer, M. C., Matlis, N. H., Leemans, W. P., McGuffey, C., Bulanov, S. S., et al. (2010) · Physical Review Letters · doi:10.1103/physrevlett.104.134801 · Cited by 45
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Raman amplifier model in single-mode optical fiber
Mandelbaum, I., & Bolshtyansky, M. A. (2003) · IEEE Photonics Technology Letters · doi:10.1109/lpt.2003.819760 · Cited by 43
Karásek, M., & Vallés, J. A. (1998) · Journal of Lightwave Technology · doi:10.1109/50.721066 · Cited by 43
Foster, S. B. (2008) · Physical Review A · doi:10.1103/physreva.78.013820 · Cited by 42
Quantum dot–quantum dot interactions mediated by a metal nanoparticle: Towards a fully quantum model
Artuso, R. D., & Bryant, G. W. (2013) · Physical Review B · doi:10.1103/physrevb.87.125423 · Cited by 42
Extra phase noise from thermal fluctuations in nonlinear optical crystals
César, J. E. S., Coelho, A. S., Cassemiro, K. N., Villar, A. S., Lassen, M., Nussenzveig, P., & Martinelli, M. (2009) · Physical Review A · doi:10.1103/physreva.79.063816 · Cited by 41
Phase-resolved time-domain nonlinear optical signals
Faeder, S. M. G., & Jonas, D. M. (2000) · Physical Review A · doi:10.1103/physreva.62.033820 · Cited by 41
Using a polarized maser to detect high-frequency relic gravitational waves
Tong, M., Zhang, Y., & Li, F.-Y. (2008) · Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D. Particles and fields · doi:10.1103/physrevd.78.024041 · Cited by 40
Secretory immune system of rabbit ocular adnexa.
Franklin, R. M., Prendergast, R. A., & SILVERSTEIN, A. (1979) · PubMed · Cited by 40
Govorov, A. O. (2010) · Physical Review B · doi:10.1103/physrevb.82.155322 · Cited by 39
Colloquium: Multiparticle quantum superpositions and the quantum-to-classical transition
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Complete achromatic optical switching between two waveguides with a sign flip of the phase mismatch
Huang, W., Rangelov, A. A., & Kyoseva, E. S. (2014) · Physical Review A · doi:10.1103/physreva.90.053837 · Cited by 36
Coherent Light with Tunable Polarization from Single-Pass Free-Electron Lasers
Spezzani, C., Allaria, E., Coreno, M., et al. (2011) · Physical Review Letters · doi:10.1103/physrevlett.107.084801 · Cited by 37
Linear azimuthons in circular fiber arrays and optical angular momentum of discrete optical vortices
Alexeyev, C. N., Volyar, A. V., & Yavorsky, M. A. (2009) · Physical Review A · doi:10.1103/physreva.80.063821 · Cited by 35
Parametric Amplification of the Dynamic Radiation Force of Acoustic Waves in Fluids
Silva, G. T., Chen, S., & Viana, L. P. (2006) · Physical Review Letters · doi:10.1103/physrevlett.96.234301 · Cited by 36
Theory of spontaneous parametric down-conversion from photonic crystals
Vamivakas, A. N., Saleh, B. E. A., Sergienko, A. V., et al. (2004) · Physical Review A · doi:10.1103/physreva.70.043810 · Cited by 36
Autoresonant Dynamics of Optical Guided Waves
Barak, A., Lamhot, Y., Frièdland, L., & Segev, M. (2009) · Physical Review Letters · doi:10.1103/physrevlett.103.123901 · Cited by 35
Degenerate four-wave mixing in triply resonant Kerr cavities
Ramirez, D. M., Rodríguez, A. W., Hashemi, H., et al. (2011) · Physical Review A · doi:10.1103/physreva.83.033834 · Cited by 34
Space-frequency coupling, conical waves, and small-scale filamentation in water
Liu, J., Schroeder, H., Chin, S. L., et al. (2005) · Physical Review A · doi:10.1103/physreva.72.053817 · Cited by 34
Influence of nanoparticle size on the nonlinear optical properties of magnetite ferrofluids
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Slow light based on population oscillation in quantum dots with inhomogeneous broadening
Chang, S., & Chuang, S. L. (2005) · Physical Review B · doi:10.1103/physrevb.72.235330 · Cited by 32
Quantum theory of spontaneous emission in multilayer dielectric structures
Creatore, C., & Andreani, L. C. (2008) · Physical Review A · doi:10.1103/physreva.78.063825 · Cited by 32
Plasmon-assisted mass sensing in a hybrid nanocrystal coupled to a nanomechanical resonator
Li, J., & Zhu, K. (2011) · Physical Review B · doi:10.1103/physrevb.83.245421 · Cited by 31
Efficient fiber coupling of down-conversion photon pairs
Dragan, A. (2004) · Physical Review A · doi:10.1103/physreva.70.053814 · Cited by 32
Metadata
- Authors
- Yariv, A., & Moos, H. W.
- Venue
- American Journal of Physics
- Published
- 1968-02-01
- Volume
- 36
- Issue
- 2
- Pages
- 168-169
- ISSN
- 0002-9505 (ISSN-L)
- 1943-2909
- OpenAlex
- W4236485540
- Cited by
- 209
- References
- 0
- Citations by year
- 2026: 1 · 2023: 2 · 2022: 1 · 2017: 1 · 2015: 4 · 2014: 10 · 2013: 8 · 2012: 9
- FWCI
- 0.00
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- American Journal of Physics (publishedVersion)
- CaltechAUTHORS (California Institute of Technology) (acceptedVersion)
- CERN Document Server (European Organization for Nuclear Research) (submittedVersion)
- Topics
- Physical Sciences › Engineering › Electrical and Electronic Engineering › Semiconductor Lasers and Optical Devices
- Physical Sciences › Physics and Astronomy › Atomic and Molecular Physics, and Optics › Photorefractive and Nonlinear Optics
- Physical Sciences › Engineering › Electrical and Electronic Engineering › Optical Systems and Laser Technology
- Keywords
- lasers, quantum electronics, semiconductor lasers, quantum well lasers, free-electron laser, laser noise, current modulation, laser arrays, supermodes, third-order nonlinear effects
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