What Is a TO-46 Package?

A definition of the TO-46 laser diode header: the 4.7 mm hermetic can for VCSEL and sensing, how it differs from TO-18, TO-56, and TO-60, and what to send for a quote.

What a TO-46 package does

A TO-46 package is a hermetic metal can that holds a small laser diode or VCSEL. Glass-to-metal pins bring power and signal out through the base, and a window or lens in the cap lets the light out. The base is about 4.7 mm, which is why it shows up in space-tight sensing and time-of-flight modules.

Hermetic housing. The cap and glass seals keep the chip in a controlled atmosphere.
Optical exit. A flat window, an AR-coated window, or a lens sets how the beam leaves the can.
Compact emitter. The 4.7 mm base fits VCSEL arrays and short-reach sensing. Lead length and the small aperture limit it to about 2 Gbit/s.

TO-46 next to the other headers

Package	Base	Speed class	Primary use
TO-46	4.7 mm	Up to about 2 Gbit/s	VCSEL, time-of-flight, compact sensing
TO-18	5.6 mm	Up to 2.5 Gbit/s	DFB, FP, pumps, industrial CW
TO-56	5.6 mm	About 10 Gbit/s	SFP-class lasers, monitor photodiode
TO-60	5.6 mm class	25 Gbit/s class	EML and coherent TOSA

The full comparison, including detector cans such as TO-5 and TO-8, is the TO header selection guide. A fiber-pigtailed DFB that needs TEC pins is a 14-pin butterfly package, not a TO-46.

What sits inside the can

The chip usually sits on a submount, not directly on the header post. An AlN submount is the common choice for a CW VCSEL or sensing laser. A SiC submount is the step up when the pulse current needs more spreading. Junction-to-case thermal resistance on a small can is often in the 200–300 K/W class, which is acceptable for sub-watt CW and tight for a high-duty pulse.

Catalog outlines and the quote form are on the TO header page. A drawing review goes through the TO header RFQ. Quotes typically return in 2–4 weeks.

The part that depends on your die

The rules above hold for most edge-emitter modules. What changes from program to program is geometry, duty cycle, and how hard you are pushing junction temperature — those inputs decide material, thickness, and whether catalog samples are enough.

Module outline, leak rate, and window transmission for your wavelength.
TEC vs uncooled budget for your channel plan.
Submount choice inside the full hermetic stack.

Go deeper — Package context

These guides answer adjacent questions teams ask while choosing a submount. Each ends the same way: what you can decide in general, then what needs your die and power.

More topics coming — thermal path, attach yield, qualification, and packaging context.

Frequently asked questions

What is a TO-46 package?

A compact hermetic transistor-outline header for a laser diode or VCSEL. The base is about 4.7 mm. It is the small emitter can used for sensing and time-of-flight, not the 10 Gbit/s or 25 Gbit/s datacom can.

How is TO-46 different from TO-56?

TO-46 is the smaller can, about 4.7 mm, for compact VCSEL and sensing up to about 2 Gbit/s. TO-56 is a 5.6 mm header used for 10 Gbit/s SFP-class lasers and usually adds a pin for a monitor photodiode.

Can FerraLink quote a TO-46 header?

Yes. Catalog TO headers, including TO-46, are quoted in 2–4 weeks. Send the die size, wavelength, window type, and whether the build needs a submount with AuSn.

Request a quote