Backward-wave optical parametric oscillators (BWOPOs) represent a significant advancement in nonlinear optics, offering unique capabilities such as narrowband, highly stable outputs without the need for mirrors or coatings. Leveraging self-established distributed feedback, these devices exhibit exceptional spectral and spatial properties. This paper explores the principles behind BWOPOs, materials and techniques used, and their applications, particularly in mid-infrared lidar systems including CO2 monitoring. Recent developments in cascaded systems and BWOPO waveguides are highlighted, demonstrating the potential of BWOPOs to revolutionize laser technology.

In this work, the development of a novel ultra-short laser system is presented, building upon previous research in passive mode-locking using cross-amplitude modulation (XAM). By combining XAM with cascaded second-order nonlinearity mode-locking (CSM) the system produced a stable bright-dark two-color output with picosecond pulses and a repetition rate of 275 MHz with an average output power of 100 mW for an 808 nm pump power of 4 W. The experimental setup involved two Nd: YVO₄ lasers operating at 1064 nm and 1342 nm, where the two cavities were interconnected with a dichroic mirror allowing for a shared section where a periodically poled KTiOPO₄ (PPKTP) was introduced. In the separate sections, the independently diode-pumped laser crystals were placed. The enhanced intra-cavity intensity achieved through XAM enabled effective pulse compression via CSM. The results demonstrate the system’s ability to generate near-transform-limited pulses as short as 14 ps, offering potential for applications such as medical imaging and LIDAR.

A lab-in-a-fiber component was fabricated using an optical fiber and a fiber capillary. It was used in a test suspension of fluorescently labeled and unlabeled cells and enabled detection of the labeled cells. Subsequently the labeled cells were selectively collected via suction into the capillary. A novel sampling technique reduced photobleaching of the labeled cells, extending the measurement time. The collected cells remained viable for downstream analysis. This platform’s low fabrication cost, simplicity, compatibility with standard laboratory equipment, and capacity for fully automated cell capture highlights its potential for future applications in minimally invasive sample collection and point-of-care diagnostics. We demonstrate this LiF device to showcase the capability of optical fiber technology in creating low-cost, low-complexity cancer diagnostic devices. Furthermore, the LiF device holds promise for in vivo diagnostics, facilitating cell isolation and analysis.

In this work, a novel 2.7 µm source used for CO2 and H2O vapor spectroscopy using the backward propagating wave of a backward wave optical parametric oscillator (BWOPO) is demonstrated for the first time to our knowledge. The unique properties of BWOPOs eliminate the need for additional spectral narrowing or wavelength stabilization, enabling the use of a multi-longitudinal mode Q-switched pump laser centered around 1030 nm. A full characterization of the source is presented, revealing a central output at 2712 nm, showcasing a temperature tuning of −1.77 GHz/K, and achieving an output pulse energy of 2.3 µJ. Novel methods are introduced for measuring the linewidth and wavelength stability using the ambient laboratory air. These approaches demonstrate a narrow output of 43 pm and establish an upper limit of stability at 65 MHz, with no active means of stabilization. These findings underscore the potential of BWOPOs as a robust platform for future differential absorption lidar (DIAL) systems.

As demand for customized specialty fibers grows, standardized production methods face challenges. This article reviews industry standards and discusses potentially disruptive techniques that enable rapid prototyping and fabrication of optical fiber devices. Furthermore, we showcase laser powder deposition's (LPD) potential for additive manufacturing (AM) of customized glass structures. In the case of, for example, fiber preforms, although the feasible size is smaller than the industry standard, utilizing laser-based manufacturing techniques for a small batch production presents an attractive avenue for rapid prototyping and expedites material and design optimization. In the realm of AM of glass, LPD offers numerous benefits, including minimal shrinkage, high densification, and the ability to tailor glass composition to achieve desired optical properties. The article reviews the latest achievements and highlights future directions in this technology.

We present backward wave optical parametric oscillator waveguides implemented in periodically poled Rb-doped KTP. The waveguides demonstrated low loss (0.16 dB/cm) and exhibited an oscillation threshold 19 times lower than the corresponding bulk device.

We present backward wave optical parametric oscillator waveguides implemented in periodically poled Rb-doped KTP. The waveguides demonstrated low loss (0.16 dB/cm) and exhibited an oscillation threshold 19 times lower than the corresponding bulk device.

The first demonstration of a 2.7 µm CO2 gas sensing source exploiting a backward wave optical parametric oscillator (BWOPO). Transmission measurements of the backward wave are demonstrated through air with good agreement with simulations.

We investigate a new method of coercive field engineering for periodic poling of RbKTiOPO4 (RKTP). By ion exchanging RKTP in a molten salt containing 7 mol% Ba(NO3)2 and 93 mol% KNO3 we achieve more than an order of magnitude difference in polarization switching time between the exchanged and non-exchanged regions. This method is used to fabricate periodic gratings of 2.92 µm in 1 mm thick bulk RKTP for second harmonic generation at 779 nm with a normalized conversion efficiency of 2%/Wcm. We show that the poled domain structures are stable at 300 °C, and that there is no bulk refractive index modification associated with the periodic ion exchange.