Have you ever felt that the very title, Progress in Optics, conjured an image in your mind? Don’t you see a row of handsomely printed books, bearing the editorial stamp of one of the most brilliant members of the optics community, and chronicling the field of optics since the invention of the laser? If so, you are certain to move the bookend to make room for Volume 16, the latest of this series. It contains seven chapters on widely diverging topics, written by well-known authorities in their fields. These are: 1) Laser Selective Photophysics and Photochemistry by V. S. Letokhov, 2) Recent Advances in Phase Profiles (sic) Generation by J. J. Clair and C. I. Abitbol, 3 ) Computer-Generated Holograms: Techniques and Applications by W.-H. Lee, 4) Speckle Interferometry by A. E. Ennos, 5 ) Deformation  Invariant, Space-Variant Optical  Pattern Recognition by D. Casasent and D. Psaltis, 6) Light Emission from High-Current Surface-Spark Discharges by R. E. Beverly, and 7) Semiclassical Radiation  Theory within a  QuantumMechanical Framework by I. R. Senitzkt. The  breadth of topic  matter  spanned  by  these  chapters makes it impossible, for this reviewer at least, to pass judgement on the comprehensiveness, relevance, and completeness of every chapter. With an editorial board as prominent as that of Progress in Optics, however, it seems hardly likely that such comments should be necessary. It should certainly be possible to take the authority of each author as credible. The only remaining judgment to be  made on these chapters is their readability. In short, what are they like to read? The first sentence of the first chapter greets the eye with an obvious typographical error: “The creation of coherent laser light source, that have tunable radiation, opened the . . . .” Two pages later we find: “When two types of atoms or molecules of different isotopic composition ( A and B ) have even one spectral line that does not overlap with others, it is pos-

Progress in optics

Highly sensitive, label-free biodetection methods have applications in both the fundamental research and healthcare diagnostics arenas. Therefore, the development of new transduction methods and the improvement of the existing methods will significantly impact these areas. A brief overview of the different types of biosensors and the critical parameters governing their performance will be given. Additionally, a more in-depth discussion of optical devices, surface functionalization methods to increase device specificity, and fluidic techniques to improve sample delivery will be reviewed.

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Label-free biological and chemical sensors

We study theoretically and experimentally the spatial intensity distribution of the zero-order Bessel beam formed by the axicon which possess a rounded tip. Such a tip generates a refracted beam that interferes with the quasi-Bessel beam created behind the axicon. In turn an undesired intensity modulation occurs that significantly disturbs the unique properties of the quasi-Bessel beam--namely the constant shape of the lateral intensity distribution and the slow variation of the on-axis beam intensity along the beam propagation. We show how the spatial filtration of the beam in the Fourier plane improves this spatial beam distribution and removes the undesired modulation. We use an efficient numerical method based on Hankel transformations to simulate the propagation of the beam behind the axicon and filter. We experimentally measure the intensity distribution of the beam in many lateral planes and subsequently reconstruct the spatial intensity distribution of the beam. Computed and measured beam distributions are compared and the obtained agreement is very good.

/pdf/high-quality-quasi-bessel-beam-generated-by-round-tip-axicon-24us00xqnc.pdf

High quality quasi-Bessel beam generated by round-tip axicon

Optical Whispering Gallery Modes (WGMs) derive their name from a famous acoustic phenomenon of guiding a wave by a curved boundary observed nearly a century ago. This phenomenon has a rather general nature, equally applicable to sound and all other waves. It enables resonators of unique properties attractive both in science and engineering. Very high quality factors of optical WGM resonators persisting in a wide wavelength range spanning from radio frequencies to ultraviolet light, their small mode volume, and tunable in- and out- coupling make them exceptionally efficient for nonlinear optical applications. Nonlinear optics facilitates interaction of photons with each other and with other physical systems, and is of prime importance in quantum optics. In this paper we review numerous applications of WGM resonators in nonlinear and quantum optics. We outline the current areas of interest, summarize progress, highlight difficulties, and discuss possible future development trends in these areas.

https://iopscience.iop.org/article/10.1088/2040-8978/18/12/123002/pdf

Nonlinear and quantum optics with whispering gallery resonators

We have constructed and tested a laser interferometer transducer for a long, wideband, laser-linked gravitational radiation antenna. Photon-noise-limited performance was achieved using 80 microW from a single mode Spectra-Physics 119 laser in a modified Michelson interferometer on a vibration isolation table in a quiet room. A piezoelectric driver on one of the interferometer mirrors was used to generate subangstrom (3 x 10(-14)-m) vibrations of known amplitude. The measured displacement sensitivity of the system in the kilohertz region was 1.3 x 10(-14)m/Hz(1/2), which compares well with the calculated photon noise limit of 1.06 x 10(-14) m/Hz(1/2). This is the smallest vibrational displacement measured directly with a laser to date.

Photon-noise-limited laser transducer for gravitational antenna

We experimentally verify uncertainty relations for mixed states in the tomographic representation by measuring the radiation field tomograms, i.e. homodyne distributions. Thermal states of single-mode radiation field are discussed in details as paradigm of mixed quantum state. By considering the connection between generalised uncertainty relations and optical tomograms is seen that the purity of the states can be retrieved by statistical analysis of the homodyne data. The purity parameter assumes a relevant role in quantum information where the effective fidelities of protocols depend critically on the purity of the information carrier states. In this contest the homodyne detector becomes an easy to handle purity-meter for the state on-line with a running quantum information protocol.

Homodyne extimation of quantum states purity by exploiting covariant uncertainty relation

Twin beams correlation and single beam noise for triply resonant KTP OPOs

Large ring-laser gyroscopes are capable of measuring angular rotations with a precision well below fractions of $prad/s$, not far from $10^{-14}$ $rad/s$, the accuracy required for General Relativity tests, this is what the GINGER (Gyroscope-IN-GEneral-Relativity) experiment is aiming for. These features do not guarantee the possibility of measuring the General Relativity Lense--Thirring effect, that manifests itself as a tiny ($\approx 10^{-9} \times \Omega_E$) perturbation of the Earth rotation rate. An underground location being in principle less affected by external local disturbances represents a good candidate for housing such a challenging experiment. GINGERino is a test apparatus to investigate the residual local disturbances in the most inner part of the underground international laboratory of the GranSasso (LNGS). It consists of a square ring laser with a $3.6$ m side. The instrument has been tailored to be the larger allowed by the particular location inside the laboratory. Its main objective is to measure the very low frequency rotational motions, in order to prove that LNGS is a suitable location for very low noise measurements and, possibly, General Relativity tests. Aside this main goal, GINGERino will provide unique data for geodesy and geophysics. Its installation has been completed during 2015. Since then, several long set of data have been collected, and the apparatus has been continuously running unattended for more than one week. The typical power spectrum sensitivity was a few $ 10^{-10} rad/s/\sqrt(Hz)$, with integration time not longer than tens of seconds. Improvements of the apparatus are ongoing in order to improve the integration time.

First Results of GINGERino, a deep underground ringlaser

An optical spring effect has been observed in the motion of a Fabry-Perot cavity suspended in the Low-Frequency Facility, R and D experiment of the VIRGO Collaboration. The experimental setup consists of a 1-cm-long cavity hanging from a mechanical isolation system, conceived to suppress seismic noise transmission to the optical components of the interferometer. The observed radiation pressure effect corresponds to an optical stiffness k{sub opt} ranging between 2.5x10{sup 4} and 6.5x10{sup 4} N/m. This paper reports several measurements of the mirror relative displacement carried out in different working conditions. The measured error signal spectra show broad resonances at frequencies compatible with the optomechanical system. In other runs cavity detuning oscillations have been observed at subhertz frequencies. In these cases the power spectrum of the control loop error signal exhibited a broad resonance with superimposed uniformly spaced peaks. These observations, validated by a simple model, prove that the fluctuations of the optical spring effect can become so large as to exhibit nonlinear features.

Experimental evidence for an optical spring

The far-field intensity pattern of laser beams diffracted by axicons is extensively characterized both theoretically and experimentally. The regular structure of the pattern, consisting of high-contrast fringes, is explained. The experimental results have been interpreted by representing the diffracted field as generated by an extended virtual source shaped as a circle centered on the optical axis of the incident laser beam. The simulations include modifications to the diffraction pattern arising from the laser radiation diffraction limit at the axicon tip, and they reproduce well the measured intensity profile at different distances from the axicon.

A. Porzio

Papers

Homodyne extimation of quantum states purity by exploiting covariant uncertainty relation

Twin beams correlation and single beam noise for triply resonant KTP OPOs

First Results of GINGERino, a deep underground ringlaser

Experimental evidence for an optical spring

Fringe pattern of the field diffracted by axicons.