We present the Twente Photoacoustic Mammoscope 2 ( PAM 2) based on a 3D tomographic geometry. A functional optical contrast map of breast vascularization can be obtained in a noninvasive, radiation-free and painless manner. A woman lies prone on a bed with one breast pendant in an imaging tank with water, where 12 curved ultrasound arrays are mounted. Each array extends from chest wall towards the nipple following the contour of the pendant breast, and carries 32 detector elements. The detectors' center frequency is 1 MHz. The breast is illuminated from multiple directions: the ventral side of the breast from the bottom and the areas close to the chest wall from the sides. The excitation wavelengths are 755 nm and 1064 nm. By rotating the imaging tank in between measurements, multiple projections can be obtained, providing a 3D image of the breast after reconstruction by means of a filtered backprojection. So far, breasts of healthy volunteers were imaged. Three-dimensional images of the breast contour, the nipple and blood vessel networks within the breast could be observed with high contrast and unprecedented detail.

We investigate the benefits of estimating the group delay spectrum (as opposed to the phase spectrum) on the performance of an adaptive laser pulse shaping experiment. We use both numerical and experimental approaches, and consider different figures of merit such as efficiency, noise robustness, convergence speed, repeatability, fitness sensitivity, and parameter insensitivity. While primarily focused on the process of broadband second harmonic generation, we also study a resonant third order nonlinear process. Our results show an overall superiority of delay-based formulation in the cases under study (compared to a conventional phase-based formulation) for adaptive laser pulse shaping.

Many spectroscopic applications of femtosecond laser pulses require properly-shaped spectral phase profiles. The optimal phase profile can be programmed on the pulse by adaptive pulse shaping. A promising optimization algorithm for such adaptive experiments is evolution strategy (ES). Here, we report a four fold increase in the rate of convergence and ten percent increase in the final yield of the optimization, compared to the direct parameterization approach, by using a new version of ES in combination with Legendre polynomials and frequency-resolved detection. Such a fast learning rate is of paramount importance in spectroscopy for reducing the artifacts of laser drift, optical degradation, and precipitation.

Photodynamic therapy (PDT) is a treatment based on the interaction of light, photosensitizing agents and tissue oxygen. The light delivery in PDT is usually optimized by controlling the intensity, the spectrum, and/or the dosage of excitation light. In this paper, we introduce a novel method that aims to improve the efficiency of PDT by controlling the phase of the excitation light, an important and so far neglected parameter. This coherent control approach utilizes the coherence properties of light-matter interaction and aims to manipulate the quantum interferences between various available reaction pathways. In general, an outcome of a photochemical reaction can be optimized by enhancing the desired reaction pathways and suppressing other unwanted pathways. Such optimizations can be done by appropriate tailoring of the electric field profile of a broadband coherent excitation light, i.e. ultrafast laser pulse. Here, we used a femtosecond laser source with adaptive pulse shaping together with a molecular feedback in a learning loop to search for and synthesize such 'smart' laser pulses. Our control objective is to enhance the triplet yield of a model photosensitizer zinc phthalocyanine (ZnPc), which then leads to enhancement of the overall PDT process. We use two coherent control schemes where we optimize the ratio between the excited singlet state (S) and triplet state (T) ZnPc molecules both ways (S/T and T/S). We demonstrate a control of 15% over the triplet yield between the found best and the worst pulse shapes. Our preliminary results show that phase shaping can indeed be used in manipulating photosensitizer photophysics and correspondingly the yield of singlet oxygen.