The diode-laser revenue figures shown in Table 2 are based on the unit sales figures in Table 1 and average selling prices (ASPs) for each type of diode laser. The ASPs for diode lasers vary widely and are a function of wavelength, power output, and package type. The revenue figures are for packaged devices as they are sold by diode-laser suppliers to the merchant market or transferred internally to other company divisions to be used in system-level products.
Diode-laser packaging is subject to a wide range of configurations according to the device type and application requirements, and includes variations such as thermal control and fiber coupling. Short-wavelength (<1000 nm) diode lasers at power levels less than 200 mW are almost always single-lateral-mode, single-stripe devices that are sold commercially in hermetically sealed TO-type packages. The lasers are typically mounted on a heat sink, and the complete package includes a back facet photodetector for monitoring the laser output level. The selling prices of such devices range from less than $1 for a high-volume CD-type laser to around $1.50 for a low-power visible (650-nm) laser, to around $7 for a 50-mW, 650-nm laser used in rewritable DVD applications. Some low-volume specialty devices can be priced much higher.
An increasingly important packaging concept in the low-power diode-laser market, originating in audio CD and CD-ROM applications that use 780-nm laser diodes, but now used widely in DVD applications that use 650-nm -laser diodes, is to carry out hybrid integration of the diode-laser chip, detector chips, and optical elements in a single package. These integrated optical pickups are lower in cost than pickups fabricated from discrete components, and result in easier assembly for the optical-disk-drive manufacturer. This concept was introduced by Sony in 1991 for its very thin (15 mm) Walkman CD player. Such pickups are now manufactured in volume by Sony, Sharp, and Matsushita, with prices around $1.60 (780 nm) to $3 (650 nm), compared to less than $1 to $2 for discrete packaged diode lasers. The value of such pickups is included in the diode-laser market units and revenues in Tables 1 and 2.
The concept of integration has also extended to combining 780-nm and 650-nm lasers in a single package. These are used in DVD players and DVD-ROM drives so that CD-type media can be read in the same drives. This type of integrated package, which is priced at around $3.30, is included in the statistics on lasers in the <700 nm category in Tables 1 and 2.
For high-power diode lasers (>1 W) there is a wide range of power levels and configurations. Up to 5-W CW, a wide (up to 500 µm) single stripe, multimode device is the norm. These devices are usually supplied in TO-type packages that can include Peltier coolers for temperature control. Beyond about 5 W, the only commonly used approach is a multistripe, multimode array. The standard product at these power levels is a 1-cm-wide diode-laser bar, which consists of a single multistripe array or a grouping of several arrays to build up higher power levels. Pricing for high-power diode lasers ranges from under $200 for a 1-W discrete device in quantity up to $2000 for a 50-W bar. Single laser bars are now available at power outputs up to 60-W CW, although 50 W is still the most common configuration. Increasingly, these high-power devices are sold with fiber coupling to provide a more usable output beam for the end user. Higher-power arrays are typically available on a heat-sink submount that can be attached to a water-cooled heat-removal system. For applications requiring high peak power, these arrays can be operated in the pulsed (quasi-CW, or QCW) mode at peak powers up to 100 W.
For power levels above 60-W CW, high-power diode-laser bars can be stacked in the vertical dimension (these products are included in the Stacks category in Tables 1 and 2). Because of the difficulty in removing heat from such a configuration, these stacks are typically operated in the QCW mode. Peak output power approaching 5 kW can be achieved from such a stack. The packages for these devices typically include water cooling, although conduction cooling may be used in lower-duty-cycle devices. With the development of more efficient heat-removal techniques (microchannel coolers, for example), CW stacks have become available.
The packages for long-wavelength (>1000 nm) diode lasers used in telecommunications applications include special adaptations for coupling the laser output to single-mode (approximately 9-µm core diameter) optical fiber with tolerances on the order of +1 µm. These are in the form of fiber pigtails or single-mode connectors. Telecommunication laser packages can also include other elements such as thermoelectric coolers for temperature control and optical isolators to reduce the amount of light reflected from the fiber back into the laser. All laser packages include back-facet-monitor photodiodes. Because of the expense of fiber coupling and other package features, telecommunications diode lasers typically have high ASPs. Prices range from less than $50 for the lowest performance 1310-nm Fabry-Perot devices in a connectorized coaxial package to $500 to $1000 for a high-performance distributed-feedback (DFB) laser in a cooled butterfly package with fiber pigtail. Diode lasers used in short-distance data-communications applications with multimode fiber have much lower prices. For example, 850-nm VCSELs packaged in several different configurations are priced at under $5.