We examine the relation between high frequency quotation and the behavior of stock prices between 2009 and 2011 for the full cross section of securities in the US. On average, higher quotation activity is associated with price series that more closely resemble a random walk, and significantly lower cost of trading. We also explore market resiliency during periods of exceptionally high low-latency trading: large liquidity drawdowns in which, within the same millisecond, trading algorithms systematically sweep large volume across multiple trading venues. Although such large drawdowns incur trading costs, they do not appear to degrade the price formation process or increase the subsequent cost of trading. In an out-of-sample analysis, we investigate an exogenous technological change to the trading environment on the Tokyo Stock Exchange that dramatically reduces latency and allows co-location of servers. This shock also results in prices more closely resembling a random walk and a sharp decline in the cost of trading.
The optical properties of intersubband transition in a semipolar AlGaN/GaN single quantum well (SQW) are theoretically studied, and the results are compared with polar c-plane and nonpolar m-plane structures. The intersubband transition frequency, dipole matrix elements, and absorption spectra are calculated for SQW on different semipolar planes. It is found that SQW on a certain group of semipolar planes (55° < θ < 90° tilted from c-plane) exhibits low transition frequency and long wavelength response with high absorption quantum efficiency, which is attributed to the weak polarization-related effects. Furthermore, these semipolar SQWs show tunable transition frequency and absorption wavelength with different quantum well thicknesses, and stable device performance can be achieved with changing barrier thickness and Al compositions. All the results indicate that the semipolar AlGaN/GaN quantum wells are promising candidate for the design and fabrication of high performance low frequency and long wavelength optoelectronic devices.