Sliding glass doors are one of the easiest ways for a burglar to enter your home so you should explore security options for this type of door. There are several types in varying prices and also tips to maintain the security of this large glass door. Since most doors are held closed with a latch rather than a lock, security options should be explored.
There is a film made by the 3M Company that blocks UV rays that can help prevent glass from shattering in windstorms and during burglaries. If a burglar tries to enter by breaking the glass and snatching items, it will hold the glass in place long enough that most seasoned burglars will opt for another home and leave yours alone. It also deters the view into your home so burglars can't see your possessions as easily through the window.
Another type of security option for your sliding glass door is a bar that extends from side to side on the non moving part of the door and locks into place. This bar is often referred to as a 'Charlie Bar'. This is one of the best devices for preventing entry by breaking the latch and forcing the door open. You can mimic this type of bar by cutting a large dowel rod or broom stick the length of the door channel and laying it horizontally in the channel. Often times, these two methods are used together. The longer it takes a burglar to enter the more likely he is to go elsewhere.
If you have an older door a burglar can actually break the latch, lift the sliding part of the door out of its channel and enter. To prevent this keep the rollers on the door adjusted to their tightest setting. You can also drill through the sliding glass door frame and into the stationary frame and install a metal pin type lock that fastens the two pieces together. These and instructions for installing them are available at your local home improvement store.