Abstract: The present invention provides compositions for making and methods of using a hand-held nucleic acid amplification device, comprising a disposable biochip with a series of sample wells, each sample well having a novel optical arrangement that includes a light-emitting diode (LED) and a single light capturing element (e.g. a photodiode) for quickly measuring light emissions from biological samples such as nucleic acid amplification reactions. Such a device can utilize isothermal amplification for obtaining detectable yields of amplified nucleic acid product in short time periods, for example, within seconds.