@article{HeuerMenzelMilonni2015,
  author    = {Heuer, Axel and Menzel, Ralf and Milonni, P. W.},
  title     = {Complementarity in biphoton generation with stimulated or induced coherence},
  series = {Physical review : A, Atomic, molecular, and optical physics},
  volume    = {92},
  journal   = {Physical review : A, Atomic, molecular, and optical physics},
  number    = {3},
  publisher = {American Physical Society},
  address   = {College Park},
  issn      = {1050-2947},
  doi       = {10.1103/PhysRevA.92.033834},
  pages     = {8},
  year      = {2015},
  abstract  = {Coherence can be induced or stimulated in parametric down-conversion using two or three crystals when, for example, the idler modes of the crystals are aligned. Previous experiments with induced coherence [Phys. Rev. Lett. 114, 053601 (2015)] focused on which-path information and the role of vacuum fields in realizing complementarity via reduced visibility in single-photon interference. Here we describe experiments comparing induced and stimulated coherence. Different single-photon interference experiments were performed by blocking one of the pump beams in a three-crystal setup. Each counted photon is emitted from one of two crystals and which-way information may or not be available, depending on the setup. Distinctly different results are obtained in the induced and stimulated cases, especially when a variable transmission filter is inserted between the crystals. A simplified theoretical model accounts for all the experimental results and is also used to address the question of whether the phases of the signal and idler fields in parametric down-conversion are correlated.},
  language  = {en}
}
@article{HeuerMenzelOstermeyer1996,
  author    = {Heuer, Axel and Menzel, Ralf and Ostermeyer, Martin},
  title     = {Power tunable Nd-oscillators with diffraction limited beams via SBS phase conjugation},
  year      = {1996},
  language  = {en}
}
@article{HeuerRaabeMenzel2014,
  author    = {Heuer, Axel and Raabe, S. and Menzel, Ralf},
  title     = {Phase memory across two single-photon interferometers including wavelength conversion},
  series = {Physical review : A, Atomic, molecular, and optical physics},
  volume    = {90},
  journal   = {Physical review : A, Atomic, molecular, and optical physics},
  number    = {4},
  publisher = {American Physical Society},
  address   = {College Park},
  issn      = {1050-2947},
  doi       = {10.1103/PhysRevA.90.045803},
  pages     = {4},
  year      = {2014},
  abstract  = {Spontaneous parametric down-conversion (SPDC) in a nonlinear crystal generates two single photons (signal and idler) with random phases. Thus, no first-order interference between them occurs. However, coherence can be induced in a cascaded setup of two crystals if, e.g., the idler modes of both crystals are aligned to be indistinguishable. Due to the effect of phase memory it is found that the first-order interference of the signal beams can be controlled by the phase delay between the pump beams. Even for pump photon delays much larger than the coherence length of the SPDC photons, the visibility is above 90\%. The high visibilities reported here prove an almost perfect phase memory effect across the two interferometers for the pump and the signal photon modes.},
  language  = {en}
}
@article{HeuerSagahtiJechowetal.2012,
  author    = {Heuer, Axel and Sagahti, A. and Jechow, Andreas and Skoczowsky, D. and Menzel, Ralf},
  title     = {Multi-wavelength, high spatial brightness operation of a phase-locked stripe-array diode laser},
  series = {Laser physics},
  volume    = {22},
  journal   = {Laser physics},
  number    = {1},
  publisher = {Pleiades Publ.},
  address   = {New York},
  issn      = {1054-660X},
  doi       = {10.1134/S1054660X12010057},
  pages     = {160 -- 164},
  year      = {2012},
  abstract  = {Stable continuous wave multi-wavelength operation of a stripe-array diode laser with an externalcavity spectral beam combining geometry is presented. In this setup each emitter of the stripe-array is forced to operate at a different wavelength, which leads to a decoupling between the usually phase-locked emitters. With a reflective diffraction grating with a period of 300 lines per mm, 33 equidistant laser lines around a center wavelength of 978 nm were realized, spanning a spectral range of 26 nm. With this novel approach near-diffraction limited emission with a beam quality of M (2) < 1.2 and an output power of 450 mW was achieved. This laser light source can be used for applications requiring low temporal but high spatial coherence.},
  language  = {en}
}
@article{HeuerSchultheissHodgsonetal.1999,
  author    = {Heuer, Axel and Schultheiss, J. and Hodgson, N. and Kurths, J{\"u}rgen and Menzel, Ralf and Raab, Volker},
  title     = {Transverse effects in phase conjugate laser mirrors based on stimulated brillouin scattering},
  year      = {1999},
  language  = {en}
}
@article{HaenischHeuerMenzel2001,
  author    = {H{\"a}nisch, Christoph and Heuer, Axel and Menzel, Ralf},
  title     = {Threshold reduction of stimulated Brillouin scattering (SBS) using fiber loop schemes},
  year      = {2001},
  language  = {en}
}
@article{JechowLichtnerMenzeletal.2009,
  author    = {Jechow, Andreas and Lichtner, Mark and Menzel, Ralf and Radziunas, Mindaugas and Skoczowsky, Danilo and Vladimirov, Andrei G.},
  title     = {Stripe-array diode-laser in an off-axis external cavity : theory and experiment},
  issn      = {1094-4087},
  doi       = {10.1364/OE.17.019599},
  year      = {2009},
  abstract  = {Stripe-array diode lasers naturally operate in an anti-phase supermode. This produces a sharp double lobe far field at angles {\~n}a depending on the period of the array. In this paper a 40 emitter gain guided stripe-array laterally coupled by off-axis filtered feedback is investigated experimentally and numerically. We predict theoretically and confirm experimentally that at doubled feedback angle 2a a stable higher order supermode exists with twice the number of emitters per array period. The theoretical model is based on time domain traveling wave equations for optical fields coupled to the carrier density equation taking into account diffusion of carriers. Feedback from the external reflector is modeled using Fresnel integration.},
  language  = {en}
}
@article{JechowLichtnerMenzeletal.2009,
  author    = {Jechow, Andreas and Lichtner, Mark and Menzel, Ralf and Radziunas, Mindaugas and Skoczowsky, Danilo and Vladimirov, Andrei G.},
  title     = {Stripe-array diode-laser in an off-axis external cavity : theory and experiment},
  issn      = {1094-4087},
  doi       = {10.1364/OE.17.019599},
  year      = {2009},
  abstract  = {Stripe-array diode lasers naturally operate in an anti-phase supermode. This produces a sharp double lobe far field at angles +/-alpha depending on the period of the array. In this paper a 40 emitter gain guided stripe-array laterally coupled by off-axis filtered feedback is investigated experimentally and numerically. We predict theoretically and confirm experimentally that at doubled feedback angle 2 alpha a stable higher order supermode exists with twice the number of emitters per array period. The theoretical model is based on time domain traveling wave equations for optical fields coupled to the carrier density equation taking into account diffusion of carriers. Feedback from the external reflector is modeled using Fresnel integration.},
  language  = {en}
}
@article{JechowRaabMenzel2006,
  author    = {Jechow, Andreas and Raab, Volker and Menzel, Ralf},
  title     = {High cw power using an external cavity for spectral beam combining of diode laser-bar emission},
  issn      = {0003-6935},
  doi       = {10.1364/AO.45.003545},
  year      = {2006},
  abstract  = {In extension to known concepts of wavelength-multiplexing diode laser arrays, a new external cavity is presented. The setup simultaneously improves the beam quality of each single emitter of a standard 25 emitter broad-area stripe laser bar and spectrally superimposes the 25 beams into one. By using this external resonator in an "off-axis" arrangement, beam qualities of M-slow(2) < 14 and M-fast(2) < 3 with optical powers in excess of 10 W in cw operation are obtained.},
  language  = {en}
}
@article{JechowSeefeldtKurzkeetal.2013,
  author    = {Jechow, Andreas and Seefeldt, Michael and Kurzke, Henning and Heuer, Axel and Menzel, Ralf},
  title     = {Enhanced two-photon excited fluorescence from imaging agents using true thermal light},
  series = {Nature photonics},
  volume    = {7},
  journal   = {Nature photonics},
  number    = {12},
  publisher = {Nature Publ. Group},
  address   = {London},
  issn      = {1749-4885},
  doi       = {10.1038/NPHOTON.2013.271},
  pages     = {973 -- 976},
  year      = {2013},
  abstract  = {Two-photon excited fluorescence (TPEF) is a standard technique in modern microscopy(1), but is still affected by photodamage to the probe. It has been proposed that TPEF can be enhanced using entangled photons(2,3), but this has proven challenging. Recently, it was shown that some features of entangled photons can be mimicked with thermal light, which finds application in ghost imaging(4), subwavelength lithography(5) and metrology(6). Here, we use true thermal light from a superluminescent diode to demonstrate TPEF that is enhanced compared to coherent light, using two common fluorophores and luminescent quantum dots, which suit applications in imaging and microscopy. We find that the TPEF rate is directly proportional to the measured(7) degree of second-order coherence, as predicted by theory. Our results show that photon bunching in thermal light can be exploited in two-photon microscopy, with the photon statistic providing a new degree of freedom.},
  language  = {en}
}