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Ultrafast adiabatic frequency conversion is a powerful method, capable of efficiently and coherently transfering ultrashort pulses between different spectral ranges, e.g. from near-infrared to mid-infrared, visible or ultra-violet. This is highly desirable in research fields that are currently limited by available ultrafast laser sources, e.g. attosecond science, strong-field physics, high-harmonic generation spectroscopy and multidimensional mid-infrared spectroscopy. Over the past decade, adiabatic frequency conversion has substantially evolved. Initially applied to quasi-monochromatic, undepleted pump interactions, it has been generalized to include ultrashort, broadband, fully-nonlinear dynamics. Through significant theoretical development and experimental demonstrations, it has delivered new capabilities and superior performance in terms of bandwidth, efficiency and robustness, as compared to other frequency conversion techniques. This article introduces the concept of adiabatic nonlinear frequency conversion, reviews its theoretical foundations, presents significant milestones and highlights contemporary ultrafast applications that may, or already do, benefit from utilizing this method.

 

We demonstrate dramatic parametric amplifier conversion efficiency enhancement simply by arranging for simultaneously phase-matched idler second-harmonic generation, with 44% pump-to-signal energy conversion (68% pump depletion) in a 48-dB-gain bulk-crystal mid-IR amplifier stage with Gaussian beams. 

We introduce a concept for efficient optical parametric amplification (OPA) based on simultaneously phase-matched idler second harmonic generation (SHG), which together exhibits the dynamical behavior of parametric amplification but with damped conversion-back-conversion cycles. This enables amplification efficiency exceeding that of conventional OPA by several-fold for femtosecond and picosecond signal pulses with bell-shaped intensity profiles by allowing a near-uniform spatiotemporal depletion of the pump wave. We develop a Duffing oscillator model that unifies the description of conventional OPA and amplification accompanied by idler photon displacement by either linear absorption or SHG. A spatiotemporal analysis of devices based on birefringent or superlattice quasi-phase matching in common bulk media predicts energy conversion up to 55%.

 

We illustrate that a Hermitian nonlinear optical system consisting of hybridized parametric amplification and second harmonic generation mimics non-Hermitian evolution dynamics. Oscillation damping, evolution to a static steady state, and exceptional points arise from the use of second harmonic generation as an irreversible loss mechanism. The investigated system can be used to solve problems of inefficiency in parametric amplifier systems used widely in laser science and industrial applications. More generally, these findings suggest a new paradigm for the engineering of system dynamics where energy recovery and system sustainability are of importance. 

Laboratory notebooks perform important roles in the engineering disciplines. They at once record an engineer’s work, serve as an important reference for future reports and/or articles, and perform as a kind of journal that enables questioning presuppositions, considering new approaches, and generating new ideas. Given the importance of notebooks, there is surprisingly little scholarship on how to teach their use. Stanley and Lewandowski (2016) surveyed students in undergraduate laboratory courses and evaluated how their notebooks were being used. They found that “few [students] … thought that their lab classes successfully taught them the benefit of maintaining a lab notebook.” Moreover, the authors’ later survey of the literature and of college faculty led them to conclude that in undergraduate lab courses “little formal attention has been paid to addressing what is considered ‘best practice’ for scientific documentation …[or] how researchers come to learn these practices” (Stanley and Lewandowski, 2018). At XXX University, two courses, Interfacing the Digital Domain with the Analog World (AEP 2640) and Engineering Communications (ENGRC 2640) are taught in conjunction. In AEP 2640, students use a computer to control equipment and acquire measurements in an engineering design and experimentation laboratory. Laboratory activities such as the development of a computer interface for an oscilloscope, a set of motors, and a photodiode culminate in the realization of an automated laser scanning microscope system. In ENGRC 2640, students receive instruction and feedback on their lab notebook entries and, in turn, use those notebooks as a resource for preparing a Progress Report and an Instrument Design Report. The instructors encourage peer review in order to facilitate improvement of students’ skills in the art of notebook use while allowing them to develop these skills and personal style through trial and error during the research. The primary learning objectives are: 1) to enable students to engage in real laboratory research; and 2) to develop proficiency with select genres associated with that research. The educational research objectives are: 1) to study students’ developing proficiency in order to generate best practices for teaching and learning scientific documentation; and 2) to better understand the contribution of scientific documentation to the teaching and learning of authentic research. This study is a work-in-progress. We will present the study design. That design involves, first, developing a self-efficacy scale for both conducting laboratory research and performing those genres associated with that research. Self-efficacy or a “person’s awareness of their ability to accomplish a goal” (Kolar et. al, 2013) has proven to be a powerful predictor of achievement. Our intent is to track learner agency. Second, the design also involves conducting a content analysis of students’ laboratory notebooks and reports. Content analysis is a methodology that encourages inferencing "across distinct domains, from particulars of one kind to particulars of another kind" (Krippendorff,, 2019). Our intent is to learn about students' mastery of the engineering design and experimentation process through analyzing their lab notebooks. We will present the results of a preliminary content analysis of a select sample of those notebooks and genres. 

By suppressing the conversion-back-conversion cycles typical of optical parametric processes through novel phase-matching schemes, octave-spanning frequency conversion and highly efficient parametric amplification can be achieved. Several recent developments will be reviewed.