A new iterative method for creating a pure phase hologram to diffract light into two arbitrary two-dimensional intensity profiles in two output planes is presented. This new method combines the GerchbergSaxton (GS) iterative algorithm and the compensation iterative algorithm. Numerical simulation indicates that the new method outperforms the most frequently used method in accuracy when it is used to generate large size images. A preliminary experiment of optical reconstruction has been taken and used to verify the feasibility of our method. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).

By using the diffractive optical elements written onto a spatial light modulator, we experimentally obtain optical regular triple-cusp beams. Their propagation characteristics and topological structures are subsequently investigated. The experimental results demonstrate that each cusp of an optical regular triple-cusp beam, similar to the main lobe of an Airy beam, propagates along curved paths in free space, hence tends to adopt the "transverse acceleration" property. Moreover, we experimentally prove that optical regular triple-cusp beams can resist local distorted deformation. Such beams can thus be applied in adverse optical environments, such as a probe for the exploration of microscopic world and as an energy source for research on high-field laser-matter interactions.

We investigate the beam quality features of an Airy beam during propagation in free space. The beam propagation factor of an Airy beam is derived based on the moments method. The results show that the beam propagation factor of an Airy beam can achieve the minimum M 2 = 1.17 when the modulation parameter a = 0.756 by compromising the effects of lateral shift, diffraction, and the departure of the main lobe of the beam with respect to the origin. Numerical calculations provide an intuitive picture to describe the propagation of an Airy beam in more detail.

It is important to monitor and assess the growth of micro-organisms under various conditions. Yet, thus far there has been no technique to do this with the required speed and accuracy. This work demonstrates swift and accurate assessment of the concentration of carbon dioxide that is produced by use of a wavelength-modulated tunable diode-laser based absorption spectroscopy (WM-TDLAS). It is shown by experiments on two types of bacteria, Staphylococcus aureus and Candida albicans, that the technique can produce high signal-to-noise-ratio data from bacteria grown in confined spaces and exposed to limited amounts of nutrients that can be used for extraction of growth parameters by fitting of the Gompertz model. By applying the technique to S. aureus bacteria at various temperatures (in the 25°C to 42°C range), it is specifically shown that both the maximum growth rate and the so-called lag time have a strong temperature dependence (under the specific conditions with a maximum of the former at 37°C) that matches conventional models well for bacterial growth. Hence, it is demonstrated that WM-TDLAS monitoring CO₂ is a user-friendly, non-intrusive, and label-free technique that swiftly, and with high signal-to-noise-ratio, can be used for rapid (on the Hz scale) and accurate assessment of bacterial growth.

Localized optical Airy-Bessel configuration wave packets were first generated on the basis of a grating-telescope combination [Nat. Photon. 4 (2010) 103]. By studying the spatially induced group velocity dispersion effect of ultrashort pulsed Bessel beams during propagation, we find the universal physical foundation of generating Airy-Bessel wave packets (ABWs) in free space. The research results are expected to open up more common channels for generating stable linear localized ABWs.