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Virtual machines (VMs) for dynamically managed languages such as JavaScript are generally implemented in C or C++. Implementation of VMs in such low-level languages offers the advantage of high flexibility, but it suffers from problems of descriptiveness and safety. These problems are due to the fact that even though a variety of VM operations are based on the VM's internal datatypes for first-class objects in the target language, the C code typically treats all VM internal datatypes as a single type in C. In addition, VMs implemented in C or C++ have a size problem which is a serious issue for VMs on embedded systems. The reason for this problem is the difficulty of eliminating unnecessary code fragments from the C code for a specific application. To solve these problems, we propose a domain-specific language for describing VM programs and a corresponding compiler to C programs, called VMDL and VMDLC, respectively. We also propose related utility tools. This framework enables generation of C source code for an eJSVM, a JavaScript VM for embedded systems. VMDL's concise syntax enables static VM datatype analysis for optimizations and error detection. We evaluated the framework and confirmed its effectiveness from both qualitative and quantitative viewpoints.

INTRODUCTIONSelf-phase modulation (SPM) is a nonlinear phenomenon widely used for broadening optical spectra in the visible to near-infrared (NIR) [1]. There have been, however, only a limited number of such reports in MIR. Corkum et al.[2] observed spectral broadening of picosecond pulses of 600-PJ energy at 9.3-Pm wavelength in semiconductor materials. Kapetanakos et al. [3] numerically studied the modulation instability inside GaAs with two closely-spaced radiation lines of a CO 2 laser. Recently, the supercontinuum extending from 0.8 Pm to 4.5 Pm has been demonstrated with ZBLAN fluoride fibers [4]. A drawback of such IR glass fibers is the difficulty in delivering high energy pulses because of the lower softening temperature. Kim et al. [5] demonstrated the supercontinuum generation at 2 ± 3.2 Pm by use of a single crystal sapphire fiber of high melting temperature. This material is useful in a range shorter than 5 Pm.Here we report that the efficient spectral broadening of MIR 100-fs pulses occurs via SPM in a GaAs single crystal. The second-order dispersion of the output pulses was compensated by the dispersive propagation in a CaF 2 plate to generate three-cycle pulses. The demonstrated scheme should work at any wavelength within the materials transparency range, and therefore be useful for spectral broadening of pulses generated from the well-established OPA-DFG system tunable around 3-18 Pm. Such MIR short pulses with broad spectra are of great importance in observing/controlling molecular vibrational dynamics.